Sampling -> Internal sensors on Nexus 7 crashes

05-23 14:12:54.046 30426-30426/fieldscience.cs.earlham.edu.fieldday E/AndroidRuntime: FATAL EXCEPTION: main Process: fieldscience.cs.earlham.edu.fieldday, PID: 30426 java.lang.RuntimeException: Unable to start activity ComponentInfo{fieldscience.cs.earlham.edu.fieldday/fieldscience.cs.earlham.edu.fieldday.SensorSampleActivity}: java.lang.NullPointerException: Attempt to invoke interface method 'int java.util.List.size()' on a null object reference at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476) at android.app.ActivityThread.-wrap11(ActivityThread.java) at android.app.ActivityThreadH.handleMessage(ActivityThread.java:1344) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:148) at android.app.ActivityThread.main(ActivityThread.java:5417) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInitMethodAndArgsCaller.run(ZygoteInit.java:726) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) Caused by: java.lang.NullPointerException: Attempt to invoke interface method 'int java.util.List.size()' on a null object reference at android.widget.ArrayAdapter.getCount(ArrayAdapter.java:337) at android.widget.ListView.setAdapter(ListView.java:491) at fieldscience.cs.earlham.edu.fieldday.SensorSampleActivity.onCreate(SensorSampleActivity.java:168) at android.app.Activity.performCreate(Activity.java:6251) at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)  at android.app.ActivityThread.-wrap11(ActivityThread.java)  at android.app.ActivityThreadH.handleMessage(ActivityThread.java:1344)  at android.os.Handler.dispatchMessage(Handler.java:102)  at android.os.Looper.loop(Looper.java:148)  at android.app.ActivityThread.main(ActivityThread.java:5417)  at java.lang.reflect.Method.invoke(Native Method)  at com.android.internal.os.ZygoteInitMethodAndArgsCaller.run(ZygoteInit.java:726)  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)