Fix issue when state value is null

Summary:
Got a string issue where data from the client was

[null]

This was blowing up in this method when we were calling Object.enties(null)

Reviewed By: antonk52

Differential Revision: D65535726

fbshipit-source-id: 9939608e3bc7e218c668cfc425b423ba0d9aee06

desktop/plugins/public/ui-debugger/ClientTypes.tsx

@@ -362,5 +362,5 @@ export type InspectableArray = {
 
 export type InspectableUnknown = {
   type: 'unknown';
-  value: string;
+  value: string | null;
 };

desktop/plugins/public/ui-debugger/components/sidebarV2/attributes/TextInput.tsx

@@ -21,10 +21,10 @@ export function StyledTextArea({
   style,
 }: {
   style?: React.CSSProperties;
-  value: string;
+  value: string | null;
   color: string;
   mutable: boolean;
-  onChange: (value: string) => void;
+  onChange: (value: string | null) => void;
   rightAddon?: string;
 }) {
   const optimisticValue = useOptimisticValue(value, onChange);
@@ -36,7 +36,7 @@ export function StyledTextArea({
       bordered
       style={{color, ...pendingStyle(optimisticValue), ...style}}
       readOnly={!mutable}
-      value={optimisticValue.value}
+      value={optimisticValue.value ?? undefined}
       onChange={(event) => optimisticValue.onChange(event.target.value)}
     />
   );