Why does javac do this?

output.javap

  public <T extends java.lang.Object> T[] toArray(T[]);
    descriptor: ([Ljava/lang/Object;)[Ljava/lang/Object;
    flags: (0x0001) ACC_PUBLIC
    Code:
      stack=2, locals=4, args_size=2
         0: aload_0
         1: getfield      #21                 // Field mutex:Ljava/lang/Object;
         4: dup
         5: astore_2
         6: monitorenter
         7: aload_0
         8: getfield      #15                 // Field c:Ljava/util/Collection;
        11: aload_1
        12: invokeinterface #41,  2           // InterfaceMethod java/util/Collection.toArray:([Ljava/lang/Object;)[Ljava/lang/Object;
        17: aload_2
        18: monitorexit
        19: areturn
        20: astore_3
        21: aload_2
        22: monitorexit
        23: aload_3
        24: athrow
      Exception table:
         from    to  target type
             7    19    20   any
            20    23    20   any // <-- why?!
      LineNumberTable:
        line 2029: 0
      LocalVariableTable:
        Start  Length  Slot  Name   Signature
            0      25     0  this   Ljava/util/Collections$SynchronizedCollection;
            0      25     1     a   [Ljava/lang/Object;
      LocalVariableTypeTable:
        Start  Length  Slot  Name   Signature
            0      25     0  this   Ljava/util/Collections$SynchronizedCollection<TE;>;
            0      25     1     a   [TT;
      StackMapTable: number_of_entries = 1
        frame_type = 255 /* full_frame */
          offset_delta = 20
          locals = [ class java/util/Collections$SynchronizedCollection, class "[Ljava/lang/Object;", class java/lang/Object ]
          stack = [ class java/lang/Throwable ]
    Signature: #129                         // <T:Ljava/lang/Object;>([TT;)[TT;