null check on intent query for InAppBillingService.

[MiketoString]

Fixes NullPointerException in IabHelperIabHelper on emulator environment where in app billing service is not available. Stack trace of error below from logcat:

D/google.payments(18242): executing on android
E/PluginManager(18242): Uncaught exception from plugin
E/PluginManager(18242): java.lang.NullPointerException: Attempt to invoke interface method 'boolean java.util.List.isEmpty()' on a null object reference
E/PluginManager(18242):     at com.alexdisler.inapppurchases.IabHelper.startSetup(IabHelper.java:276)
E/PluginManager(18242):     at com.alexdisler.inapppurchases.InAppBillingV3.init(InAppBillingV3.java:184)
E/PluginManager(18242):     at com.alexdisler.inapppurchases.InAppBillingV3.execute(InAppBillingV3.java:162)
E/PluginManager(18242):     at org.apache.cordova.CordovaPlugin.execute(CordovaPlugin.java:98)
E/PluginManager(18242):     at org.apache.cordova.PluginManager.exec(PluginManager.java:133)
E/PluginManager(18242):     at org.apache.cordova.CordovaBridge.jsExec(CordovaBridge.java:59)
E/PluginManager(18242):     at org.apache.cordova.engine.SystemExposedJsApi.exec(SystemExposedJsApi.java:41)
E/PluginManager(18242):     at com.android.org.chromium.base.SystemMessageHandler.nativeDoRunLoopOnce(Native Method)
E/PluginManager(18242):     at com.android.org.chromium.base.SystemMessageHandler.handleMessage(SystemMessageHandler.java:28)
E/PluginManager(18242):     at android.os.Handler.dispatchMessage(Handler.java:102)
E/PluginManager(18242):     at android.os.Looper.loop(Looper.java:135)
E/PluginManager(18242):     at android.os.HandlerThread.run(HandlerThread.java:61)

[coveralls]

Coverage decreased (-8.2%) to 76.471% when pulling 5c8ebe0 on MiketoString:master into 27262e5 on AlexDisler:master.