If a CompilerThread is not compiling anything, its env() will be null; same reflected in SA. No problem.

clhsdb_session

$ $JAVA_HOME/bin/java -version
java version "1.7.0_05"
Java(TM) SE Runtime Environment (build 1.7.0_05-b06)
Java HotSpot(TM) 64-Bit Server VM (build 23.1-b03, mixed mode)
$ jps
15245 JConsole
15269 Jps
$ sudo $JAVA_HOME/bin/java -cp $JAVA_HOME/lib/sa-jdi.jar sun.jvm.hotspot.CLHSDB
hsdb> attach 15245
Attaching to process 15245, please wait...
hsdb> dumpideal -a
sun.jvm.hotspot.runtime.CompilerThread@0x00007f76e40ec000
  not compiling
sun.jvm.hotspot.runtime.CompilerThread@0x00007f76e40e9800
  not compiling
hsdb> jseval "ct = sapkg.runtime.CompilerThread(any2addr(0x00007f76e40ec000))"
sun.jvm.hotspot.runtime.CompilerThread@0x00007f76e40ec000 
hsdb> jseval "ct.env()" //=> null
hsdb> jseval "c = ct.getClass()"
class sun.jvm.hotspot.runtime.CompilerThread 
hsdb> jseval "f = c.getDeclaredField('_env_field')"
private static sun.jvm.hotspot.types.AddressField sun.jvm.hotspot.runtime.CompilerThread._env_field 
hsdb> jseval "f.setAccessible(true)"
hsdb> jseval "a = f.get(ct)"
sun.jvm.hotspot.types.basic.BasicAddressFieldWrapper@63a4c4cb 
hsdb> jseval "c = a.getClass()"
class sun.jvm.hotspot.types.basic.BasicAddressFieldWrapper 
hsdb> jseval "f = c.getSuperclass()"
class sun.jvm.hotspot.types.basic.BasicFieldWrapper 
hsdb> jseval "f = f.getDeclaredField('field')"
protected sun.jvm.hotspot.types.Field sun.jvm.hotspot.types.basic.BasicFieldWrapper.field 
hsdb> jseval "f.setAccessible(true)"
hsdb> jseval "f.get(a)"
sun.jvm.hotspot.types.basic.BasicField@357185c8 
hsdb> jseval "a = f.get(a)"
sun.jvm.hotspot.types.basic.BasicField@357185c8 
hsdb> jseval "a.getOffset()"
928.0 
hsdb> jseval "a.isStatic()"
hsdb> jseval "a.getAddress(any2addr(0x00007f76e40ec000))"
hsdb> mem 0x00007f76e40ec000 200
0x00007f76e40ec000: 0x00007f76e9dadbb0 
0x00007f76e40ec008: 0x0000000000000000 
0x00007f76e40ec010: 0x0000000000000000 
0x00007f76e40ec018: 0x0000000000000000 
0x00007f76e40ec020: 0x00007f76e40ebf20 
0x00007f76e40ec028: 0x00007f76e40ecee0 
0x00007f76e40ec030: 0x0000000000000000 
0x00007f76e40ec038: 0x00007f76a80008f0 
0x00007f76e40ec040: 0x00007f76a8000a30 
0x00007f76e40ec048: 0x00007f76d6412b70 
0x00007f76e40ec050: 0x0000000000000000 
0x00007f76e40ec058: 0x0000000000000000 
0x00007f76e40ec060: 0x0000000000000000 
0x00007f76e40ec068: 0x0000000000000000 
0x00007f76e40ec070: 0x0000000000000000 
0x00007f76e40ec078: 0x00000000000027b0 
0x00007f76e40ec080: 0x000000000000009e 
0x00007f76e40ec088: 0x0000000000000000 
0x00007f76e40ec090: 0x0000000000000000 
0x00007f76e40ec098: 0x3f0334e800000000 
0x00007f76e40ec0a0: 0x0000002300000002 
0x00007f76e40ec0a8: 0x000000003ccd8f7d 
0x00007f76e40ec0b0: 0x00000000000003a0 
0x00007f76e40ec0b8: 0x0000000000000000 
0x00007f76e40ec0c0: 0x0000000000000000 
0x00007f76e40ec0c8: 0x0000000000000000 
0x00007f76e40ec0d0: 0x0000000000000001 
0x00007f76e40ec0d8: 0x0000000000000000 
0x00007f76e40ec0e0: 0x00007f76b8003b60 
0x00007f76e40ec0e8: 0x000000310000000f 
0x00007f76e40ec0f0: 0x0000000000000000 
0x00007f76e40ec0f8: 0x0000000000000000 
0x00007f76e40ec100: 0x00007f76e40ed8c0 
0x00007f76e40ec108: 0x00007f76e40130e0 
0x00007f76e40ec110: 0x00007f76e4013500 
0x00007f76e40ec118: 0x00007f76d6414000 
0x00007f76e40ec120: 0x0000000000101000 
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0x00007f76e40ec138: 0x0000000000000000 
0x00007f76e40ec140: 0x0000000000002bad 
0x00007f76e40ec148: 0x00007f76e40ed000 
0x00007f76e40ec150: 0x00007f76e40ed200 
0x00007f76e40ec158: 0x00007f76e40ed400 
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0x00007f76e40ec168: 0x0000000000000000 
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0x00007f76e40ec1d8: 0x00007f76e9dc35c0 
0x00007f76e40ec1e0: 0x0000000000000000 
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0x00007f76e40ec250: 0x000000000000000a 
0x00007f76e40ec258: 0x00007f76e4013570 
0x00007f76e40ec260: 0x0000000000000000 
0x00007f76e40ec268: 0x000000000000deab 
0x00007f76e40ec270: 0x0000000000000000 
0x00007f76e40ec278: 0x0000000200000001 
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0x00007f76e40ec288: 0x0000000000000000 
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0x00007f76e40ec2a8: 0x0000000000000000 
0x00007f76e40ec2b0: 0x00007f76e9dabeb0 
0x00007f76e40ec2b8: 0x00007f76e9dfdf20 
0x00007f76e40ec2c0: 0x0000000000000000 
0x00007f76e40ec2c8: 0x0000000000000000 
0x00007f76e40ec2d0: 0x0000000000000000 
0x00007f76e40ec2d8: 0x0000000000000000 
0x00007f76e40ec2e0: 0x0000000000000000 
0x00007f76e40ec2e8: 0x0000000000000000 
0x00007f76e40ec2f0: 0x00007f76e9d9dc50 
0x00007f76e40ec2f8: 0x00007f76e9dfdfe0 
0x00007f76e40ec300: 0x0000000000000001 
0x00007f76e40ec308: 0x0000000000000000 
0x00007f76e40ec310: 0x0000000000000000 
0x00007f76e40ec318: 0x0000000000000000 
0x00007f76e40ec320: 0x0000000000000000 
0x00007f76e40ec328: 0x0000000000000000 
0x00007f76e40ec330: 0x0000000000000000 
0x00007f76e40ec338: 0x0000000000000000 
0x00007f76e40ec340: 0x0000000000000000 
0x00007f76e40ec348: 0x0000000000000000 
0x00007f76e40ec350: 0x0000000000000000 
0x00007f76e40ec358: 0x0000000000000000 
0x00007f76e40ec360: 0x0000000000000000 
0x00007f76e40ec368: 0x0000000000000000 
0x00007f76e40ec370: 0x00007f76e40ed720 
0x00007f76e40ec378: 0x0000000000000000 
0x00007f76e40ec380: 0x00007f76e40ed840 
0x00007f76e40ec388: 0x0000000000000000 
0x00007f76e40ec390: 0x00000000ffffffff 
0x00007f76e40ec398: 0x00007f76e40eb150 
0x00007f76e40ec3a0: 0x0000000000000000 //<- ciEnv* CompilerThread::_env
0x00007f76e40ec3a8: 0x0000000000000000 
0x00007f76e40ec3b0: 0x0000000000000000 
0x00007f76e40ec3b8: 0x00007f76e40e8d40 
0x00007f76e40ec3c0: 0x0000000000000000 
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0x00007f76e40ec4b0: 0x0000000000000000 
0x00007f76e40ec4b8: 0x0000000000000000 
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0x00007f76e40ec4e0: 0x0000000000000000 
0x00007f76e40ec4e8: 0x0000000000000000 
0x00007f76e40ec4f0: 0x0000000000000000 
0x00007f76e40ec4f8: 0x0000000000000000 
0x00007f76e40ec500: 0x0000000000000000 
0x00007f76e40ec508: 0x0000000000000000 
0x00007f76e40ec510: 0x0000000000000000 
0x00007f76e40ec518: 0x0000000000000000 
0x00007f76e40ec520: 0x0000000000000000 
0x00007f76e40ec528: 0x0000000000000000 
0x00007f76e40ec530: 0x0000000000000000 
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0x00007f76e40ec608: 0x0000000000000000 
0x00007f76e40ec610: 0x0000000000000000 
0x00007f76e40ec618: 0x0000000000000000 
0x00007f76e40ec620: 0x0000000000000000 
0x00007f76e40ec628: 0x0000000000000000 
0x00007f76e40ec630: 0x0000000000000000 
0x00007f76e40ec638: 0x0000000000000000 

hsdb>