if context is null, try to get set it

src/main/java/com/owncloud/android/MainApp.java

@@ -193,6 +193,10 @@ public class MainApp extends MultiDexApplication {
         return MainApp.mContext;
     }
 
+    public static void setAppContext(Context context) {
+        MainApp.mContext = context;
+    }
+
     public static String getStoragePath() {
         return MainApp.storagePath;
     }

src/main/java/com/owncloud/android/services/observer/FileObserverService.java

@@ -168,13 +168,13 @@ public class FileObserverService extends Service {
             return Service.START_STICKY;
 
         } else if (ACTION_ADD_OBSERVED_FILE.equals(intent.getAction())) {
-            OCFile file = (OCFile) intent.getParcelableExtra(ARG_FILE);
-            Account account = (Account) intent.getParcelableExtra(ARG_ACCOUNT);
+            OCFile file = intent.getParcelableExtra(ARG_FILE);
+            Account account = intent.getParcelableExtra(ARG_ACCOUNT);
             addObservedFile(file, account);
 
         } else if (ACTION_DEL_OBSERVED_FILE.equals(intent.getAction())) {
-            removeObservedFile((OCFile) intent.getParcelableExtra(ARG_FILE),
-                    (Account) intent.getParcelableExtra(ARG_ACCOUNT));
+            removeObservedFile(intent.getParcelableExtra(ARG_FILE),
+                    intent.getParcelableExtra(ARG_ACCOUNT));
 
         } else {
             Log_OC.e(TAG, "Unknown action received; ignoring it: " + intent.getAction());
@@ -193,6 +193,10 @@ public class FileObserverService extends Service {
     private void startObservation() {
         Log_OC.d(TAG, "Loading all kept-in-sync files from database to start watching them");
 
+        if (MainApp.getAppContext() == null) {
+            MainApp.setAppContext(getApplicationContext());
+        }
+
         // query for any favorite file in any OC account
         Cursor cursorOnKeptInSync = getContentResolver().query(
                 ProviderTableMeta.CONTENT_URI,