Prevent forwarding polls (#7819)

src/components/views/context_menus/MessageContextMenu.tsx

@@ -516,7 +516,10 @@ export default class MessageContextMenu extends React.Component<IProps, IState>
 }
 
 function canForward(event: MatrixEvent): boolean {
-    return !isLocationEvent(event);
+    return !(
+        isLocationEvent(event) ||
+        M_POLL_START.matches(event.getType())
+    );
 }
 
 function isLocationEvent(event: MatrixEvent): boolean {