Workspace member can be null (#12597)

Following https://github.com/twentyhq/twenty/pull/12110
Fixes https://github.com/twentyhq/twenty/issues/12594

packages/twenty-server/src/engine/core-modules/user/user.resolver.ts

@@ -201,7 +201,7 @@ export class UserResolver {
     );
 
     if (!isDefined(workspaceMemberEntity)) {
-      throw new Error('Workspace member not found');
+      return null;
     }
 
     const workspaceId = workspace.id;