Crash on Realm on a clean install.

Categeory.java

Public class Category extends RealmObject {
    @PrimaryKey
    private String title;

    public String getTitle() { return title; }
    public void setTitle(String t) { this.title = t; }
}

Crash.txt

08-13 17:13:35.186 12274 12274 E AndroidRuntime: java.lang.RuntimeException: Unable to start activity ComponentInfo{io.errorlab.slickbackgrounds/io.errorlab.slickbackgrounds.activities.MainActivity}: io.realm.exceptions.RealmMigrationNeededException: RealmMigration must be provided
08-13 17:13:35.186 12274 12274 E AndroidRuntime: 	at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2417)
08-13 17:13:35.186 12274 12274 E AndroidRuntime: 	at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2477)
08-13 17:13:35.186 12274 12274 E AndroidRuntime: 	at android.app.ActivityThread.-wrap11(ActivityThread.java)
08-13 17:13:35.186 12274 12274 E AndroidRuntime: 	at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1345)
08-13 17:13:35.186 12274 12274 E AndroidRuntime: 	at android.os.Handler.dispatchMessage(Handler.java:102)
08-13 17:13:35.186 12274 12274 E AndroidRuntime: 	at android.os.Looper.loop(Looper.java:148)
08-13 17:13:35.186 12274 12274 E AndroidRuntime: 	at android.app.ActivityThread.main(ActivityThread.java:5415)
08-13 17:13:35.186 12274 12274 E AndroidRuntime: 	at java.lang.reflect.Method.invoke(Native Method)
08-13 17:13:35.186 12274 12274 E AndroidRuntime: 	at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:725)
08-13 17:13:35.186 12274 12274 E AndroidRuntime: 	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:615)
08-13 17:13:35.186 12274 12274 E AndroidRuntime: Caused by: io.realm.exceptions.RealmMigrationNeededException: RealmMigration must be provided
08-13 17:13:35.186 12274 12274 E AndroidRuntime: 	at io.realm.Realm.migrateRealm(Realm.java:1651)
08-13 17:13:35.186 12274 12274 E AndroidRuntime: 	at io.realm.Realm.migrateRealm(Realm.java:1636)
08-13 17:13:35.186 12274 12274 E AndroidRuntime: 	at io.realm.Realm.create(Realm.java:569)
08-13 17:13:35.186 12274 12274 E AndroidRuntime: 	at io.realm.Realm.getInstance(Realm.java:411)
08-13 17:13:35.186 12274 12274 E AndroidRuntime: 	at io.realm.Realm.getInstance(Realm.java:368)
08-13 17:13:35.186 12274 12274 E AndroidRuntime: 	at io.realm.Realm.getInstance(Realm.java:349)
08-13 17:13:35.186 12274 12274 E AndroidRuntime: 	at io.errorlab.slickbackgrounds.activities.MainActivity.onCreate(MainActivity.java:77)
08-13 17:13:35.186 12274 12274 E AndroidRuntime: 	at android.app.Activity.performCreate(Activity.java:6162)
08-13 17:13:35.186 12274 12274 E AndroidRuntime: 	at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107)
08-13 17:13:35.186 12274 12274 E AndroidRuntime: 	at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2370)
08-13 17:13:35.186 12274 12274 E AndroidRuntime: 	... 9 more

Wallpaper.java

public class Wallpaper extends RealmObject {
    @PrimaryKey
    private String id;
    
    private String title;
    private int price;
    private String author;
    private String category;
    private String thumbnail;
    private String preview;
    private String crop;
    private int width;
    private int height;

    public String getId() { return id; };
    public void setId(String id) { this.id = id; };
    
    public String getTitle() { return title; };
    public void setTitle(String title) { this.title = title; }

    public int getPrice() { return price; };
    public void setPrice(int p) { this.price = p; }
    
    public String getAuthor() { return author; }
    public void setAuthor(String s) { this.author = s; }

    public String getCategory() { return category; }
    public void setCategory(String c) { this.category = c; }

    public String getThumbnail() { return thumbnail; }
    public void setThumbnail(String t) { this.thumbnail = t; }

    public String getPreview() { return preview; }
    public void setPreview(String p) { this.preview = p; }

    public String getCrop() { return crop; }
    public void setCrop(String c) { this.crop = c; }

    public int getWidth() { return width; }
    public void setWidth(int w) { this.width = w; }

    public int getHeight() { return height; }
    public void setHeight(int h) { this.height = h; }
}