robust SpeedSearchMenu size measurement

In the CI environment, the resize observer behaves differently, and the resize callback is not initially called, leaving the lastSize ref with the default arbitrary value of `{width: 0, height: 0}`.
Not sure what makes useResizeObserver behave differently,
but the code now makes more sense regardless.

packages/jui/src/Menu/SpeedSearchMenu.tsx

@@ -127,27 +127,38 @@ function useSpeedSearchMenu<T>(
     }
   });
 
-  const lastSize = useRef({ width: 0, height: 0 });
+  const lastSize = useRef<{ width: number; height: number } | null>(null);
   const [size, setSize] = useState<{ width: number; height: number } | null>(
     null
   );
+  const measureSize = () => {
+    const { offsetWidth = 0, offsetHeight = 0 } = containerRef.current || {};
+    if (offsetWidth > 0 && offsetHeight > 0) {
+      lastSize.current = {
+        width: offsetWidth,
+        height: offsetHeight,
+      };
+    }
+  };
   const isSearchActive =
     speedSearch.active && speedSearch.searchTerm.length > 0;
   useResizeObserver({
     ref: containerRef,
     onResize: useEventCallback(() => {
       if (!isSearchActive) {
-        lastSize.current = {
-          width: containerRef.current?.offsetWidth ?? 0,
-          height: containerRef.current?.offsetHeight ?? 0,
-        };
+        measureSize();
       }
     }),
   });
   useLayoutEffect(() => {
     if (isSearchActive) {
-      setSize(lastSize.current);
+      if (lastSize.current) {
+        setSize(lastSize.current);
+      }
     } else {
+      if (!lastSize.current) {
+        measureSize();
+      }
       setSize(null);
     }
   }, [isSearchActive]);