fix(core): don't set editor content if value is undefined #441 (#442)

Author: mrdrogdrog

core/src/useCodeMirror.ts

@@ -181,6 +181,9 @@ export function useCodeMirror(props: UseCodeMirror) {
  ]);
 
  useEffect(() => {
+ if (value === undefined) {
+ return;
+ }
  const currentValue = view ? view.state.doc.toString() : '';
  if (view && value !== currentValue) {
  view.dispatch({