fix(react/dialogs): some type errors

apps/client/src/widgets/react/react_utils.ts

@@ -0,0 +1,15 @@
+import type { RefObject } from "preact";
+
+/**
+ * Takes in a React ref and returns a corresponding JQuery selector.
+ *
+ * @param ref the React ref from which to obtain the jQuery selector.
+ * @returns the corresponding jQuery selector.
+ */
+export function refToJQuerySelector<T extends HTMLElement>(ref: RefObject<T> | null): JQuery<T> {
+    if (ref?.current) {
+        return $(ref.current);
+    } else {
+        return $();
+    }
+}