fix: ensure non-null resolver value in Editor (#566)

Author: ismajl-ramadani

.changeset/funny-shoes-begin.md

@@ -0,0 +1,5 @@
+---
+'@craftjs/core': patch
+---
+
+Ensure non-null resolver prop value in Editor component

packages/core/src/editor/Editor.tsx

@@ -18,7 +18,9 @@ export const Editor: React.FC<React.PropsWithChildren<Partial<Options>>> = ({
   // we do not want to warn the user if no resolver was supplied
   if (options.resolver !== undefined) {
     invariant(
-      typeof options.resolver === 'object' && !Array.isArray(options.resolver),
+      typeof options.resolver === 'object' &&
+        !Array.isArray(options.resolver) &&
+        options.resolver !== null,
       ERROR_RESOLVER_NOT_AN_OBJECT
     );
   }