persist pointerDown event (#1426)

src/components/App.tsx

@@ -1577,6 +1577,8 @@ class App extends React.Component<any, AppState> {
   private handleCanvasPointerDown = (
     event: React.PointerEvent<HTMLCanvasElement>,
   ) => {
+    event.persist();
+
     if (lastPointerUp !== null) {
       // Unfortunately, sometimes we don't get a pointerup after a pointerdown,
       // this can happen when a contextual menu or alert is triggered. In order to avoid