fix NullPointerException

java.lang.RuntimeException: Unable to start activity
ComponentInfo{giraffine.dimmer/giraffine.dimmer.SettingsActivity}:
java.lang.NullPointerException
at
android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2198)
at
android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2248)
at android.app.ActivityThread.access$800(ActivityThread.java:138)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1199)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5050)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at
com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
at de.robv.android.xposed.XposedBridge.main(XposedBridge.java:132)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
at giraffine.dimmer.Prefs.getWidgetMode(Prefs.java:76)
at giraffine.dimmer.SettingsFragment.onCreate(SettingsFragment.java:54)
at android.app.Fragment.performCreate(Fragment.java:1678)
at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:859)
at
android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1062)
at android.app.BackStackRecord.run(BackStackRecord.java:684)
at
android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1447)
at android.app.Activity.performStart(Activity.java:5250)
at
android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2171)
... 12 more