fix: stabilize the fallback value of useXarrow

Before effects have fired, useXarrow() will return a new reference every render. This can lead to a render loop if updateXarrow is placed in a hook's dependency list. Stabilize it by making the fallback value a module-scope const.

Author: Alexandra Parker

src/useXarrow.tsx

@@ -1,12 +1,14 @@
 import React, { useContext, useLayoutEffect, useState } from 'react';
 import { XelemContext } from './Xwrapper';
 
+const noop = () => {};
+
 const useXarrow = () => {
   const [, setRender] = useState({});
   const reRender = () => setRender({});
 
   let updateXarrow = useContext(XelemContext);
-  if (!updateXarrow) updateXarrow = () => {};
+  if (!updateXarrow) updateXarrow = noop;
   // throw new Error(
   //   "'Xwrapper' is required around element using 'useXarrow' hook! wrap your xarrows and connected elements with Xwrapper! "
   // );