fix(environment-variable): guard refresh against missing or stale variables

Add early return in refresh() to skip sync operations if the environment variable no longer exists or is not fresh, preventing errors when refreshing stale or deleted variables.

app/Livewire/Project/Shared/EnvironmentVariable/Show.php

@@ -98,6 +98,9 @@ class Show extends Component
 
     public function refresh()
     {
+        if (! $this->env->exists || ! $this->env->fresh()) {
+            return;
+        }
         $this->syncData();
         $this->checkEnvs();
     }