Fix form cached subscribe status

app/Models/Forms/Form.php

@@ -146,8 +146,8 @@ class Form extends Model implements CachableAttributes
 
     public function getIsProAttribute()
     {
-        return $this->remember('is_pro', 15 * 60, function (): bool {
-            return optional($this->workspace)->is_pro;
+        return $this->remember('is_pro', 15 * 60, function (): ?bool {
+            return optional($this->workspace)->is_pro === true;
         });
     }