Prevent app from crashing when getCurrentActivity is null

Summary:
We're seeing a lot of crashes from `PermissionsModule` not being able to access the current activity, mentioned in facebook#10009 and here: facebook#9310 (comment)

As far as I can tell, there is no way to ensure the Activity exists since the `ReactContext` holds a `WeakReference` to the current Activity and it appears that the lifecycle calls are happening in the right order (so not the same as facebook#9310).

This will at least allow people to catch the error in JS and update the UI or try again as opposed to crashing the app.

I'm working on some bigger changes in facebook#10221 but this is a smaller change and important to get fixed I think.
Closes facebook#10351

Differential Revision: D4010242

fbshipit-source-id: 7a76973bb2b3e45817d4283917740c89a10ec0b0

ReactAndroid/src/main/java/com/facebook/react/modules/permissions/PermissionsModule.java

@@ -31,6 +31,7 @@
 @ReactModule(name = "PermissionsAndroid")
 public class PermissionsModule extends ReactContextBaseJavaModule implements PermissionListener {
 
+  private static final String ERROR_INVALID_ACTIVITY = "E_INVALID_ACTIVITY";
   private final SparseArray<Callback> mCallbacks;
   private int mRequestCode = 0;
 
@@ -73,7 +74,11 @@ public void shouldShowRequestPermissionRationale(final String permission, final
       promise.resolve(false);
       return;
     }
-    promise.resolve(getPermissionAwareActivity().shouldShowRequestPermissionRationale(permission));
+    try {
+      promise.resolve(getPermissionAwareActivity().shouldShowRequestPermissionRationale(permission));
+    } catch (IllegalStateException e) {
+      promise.reject(ERROR_INVALID_ACTIVITY, e);
+    }
   }
 
   /**
@@ -95,17 +100,22 @@ public void requestPermission(final String permission, final Promise promise) {
       return;
     }
 
-    mCallbacks.put(
+    try {
+      PermissionAwareActivity activity = getPermissionAwareActivity();
+
+      mCallbacks.put(
         mRequestCode, new Callback() {
           @Override
           public void invoke(Object... args) {
             promise.resolve(args[0].equals(PackageManager.PERMISSION_GRANTED));
           }
         });
 
-    PermissionAwareActivity activity = getPermissionAwareActivity();
-    activity.requestPermissions(new String[]{permission}, mRequestCode, this);
-    mRequestCode++;
+      activity.requestPermissions(new String[]{permission}, mRequestCode, this);
+      mRequestCode++;
+    } catch (IllegalStateException e) {
+      promise.reject(ERROR_INVALID_ACTIVITY, e);
+    }
   }
 
   /**