fix error caused by first argument short when calling warning function

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My app crashed when I call navigator.geolocation.stopObserving(). I found it is caused by the reason that one argument short. So I added false to the first argument. Then bug is fixed.

1. call both navigator.geolocation.watchPosition and navigator.geolocation.getCurrentPosition
2. then call navigator.geolocation.stopObserving()
3. error happened before I fixed, and correct Warning "Called stopObserving with existing subscriptions." shown after I fixed.
Closes https://github.com/facebook/react-native/pull/14673

Differential Revision: D5301503

Pulled By: javache

fbshipit-source-id: 9e85064beb1052bb89bf42355ffd308fe9eaec53

Libraries/Geolocation/Geolocation.js

@@ -175,7 +175,7 @@ var Geolocation = {
       for (var ii = 0; ii < subscriptions.length; ii++) {
         var sub = subscriptions[ii];
         if (sub) {
-          warning('Called stopObserving with existing subscriptions.');
+          warning(false, 'Called stopObserving with existing subscriptions.');
           sub[0].remove();
           // array element refinements not yet enabled in Flow
           var sub1 = sub[1]; sub1 && sub1.remove();