fix project deletion and refactor some code

app/Http/Controllers/Api/ProjectController.php

@@ -423,7 +423,7 @@ class ProjectController extends Controller
         if (! $project) {
             return response()->json(['message' => 'Project not found.'], 404);
         }
-        if ($project->resource_count() > 0) {
+        if (! $project->isEmpty()) {
             return response()->json(['message' => 'Project has resources, so it cannot be deleted.'], 400);
         }