-Fixed popup player not in foreground when opened by external intent.

-Fixed popup overlay permission causing exception when opened externally.

app/src/main/java/org/schabi/newpipe/RouterPopupActivity.java

@@ -21,6 +21,7 @@ public class RouterPopupActivity extends RouterActivity {
         if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M
                 && !PermissionHelper.checkSystemAlertWindowPermission(this)) {
             Toast.makeText(this, R.string.msg_popup_permission, Toast.LENGTH_LONG).show();
+            finish();
             return;
         }
         StreamingService service;