assign mAccountManager in onCreate()

Signed-off-by: tobiasKaminsky <tobias@kaminsky.me>

src/main/java/com/owncloud/android/ui/activity/ReceiveExternalFilesActivity.java

@@ -171,6 +171,7 @@ public class ReceiveExternalFilesActivity extends FileActivity
             
             mFile = savedInstanceState.getParcelable(KEY_FILE);
         }
+        mAccountManager = (AccountManager) getSystemService(Context.ACCOUNT_SERVICE);
 
         super.onCreate(savedInstanceState);
 
@@ -194,8 +195,6 @@ public class ReceiveExternalFilesActivity extends FileActivity
 
     @Override
     protected void setAccount(Account account, boolean savedAccount) {
-        mAccountManager = (AccountManager) getSystemService(Context.ACCOUNT_SERVICE);
-
         Account[] accounts = mAccountManager.getAccountsByType(MainApp.getAccountType(this));
         if (accounts.length == 0) {
             Log_OC.i(TAG, "No ownCloud account is available");