Android: pickFile() should be patched for the case when selection is cancelled, and thus messages a null URI

[birdofpreyru]

react-native-fs/android/src/main/java/com/drpogodin/reactnativefs/ReactNativeFsModule.java

Lines 92 to 96 in 9d5f81f

	public void onActivityResult(Uri uri) {
	WritableArray res = Arguments.createArray();
	res.pushString(uri.toString());
	pendingPickFilePromises.pop().resolve(res);
	}

☝️ Here, we should guard against uri being null.