Prevent useContextMenu isOpen from being true if the button ref goes away

src/components/structures/ContextMenu.tsx

@@ -579,7 +579,7 @@ export const useContextMenu = <T extends any = HTMLElement>(): ContextMenuTuple<
         setIsOpen(false);
     };
 
-    return [isOpen, button, open, close, setIsOpen];
+    return [button.current && isOpen, button, open, close, setIsOpen];
 };
 
 // XXX: Deprecated, used only for dynamic Tooltips. Avoid using at all costs.

src/components/views/rooms/ReadReceiptGroup.tsx

@@ -209,7 +209,8 @@ export function ReadReceiptGroup(
                     onMouseOver={showTooltip}
                     onMouseLeave={hideTooltip}
                     onFocus={showTooltip}
-                    onBlur={hideTooltip}>
+                    onBlur={hideTooltip}
+                >
                     { remText }
                     <span
                         className="mx_ReadReceiptGroup_container"