fix value formatting of proxies of class instances

For Hookstate Proxies of classes, `data.constructor.name` returns
`Proxy({})`, so use `Object.getPrototypeOf(data).constructor.name`
instead in that case.

Author: LoganDark

packages/react-devtools-shared/src/utils.js

@@ -915,7 +915,25 @@ export function formatDataForPreview(
     case 'date':
       return data.toString();
     case 'class_instance':
-      return data.constructor.name;
+      try {
+        let resolvedConstructorName = data.constructor.name;
+        if (typeof resolvedConstructorName === 'string') {
+          return resolvedConstructorName;
+        }
+
+        resolvedConstructorName = Object.getPrototypeOf(data).constructor.name;
+        if (typeof resolvedConstructorName === 'string') {
+          return resolvedConstructorName;
+        }
+
+        try {
+          return truncateForDisplay(String(data));
+        } catch (error) {
+          return 'unserializable';
+        }
+      } catch (error) {
+        return 'unserializable';
+      }
     case 'object':
       if (showFormattedValue) {
         const keys = Array.from(getAllEnumerableKeys(data)).sort(alphaSortKeys);