minor fix and update

app/Models/Applications/Application.php

@@ -97,13 +97,19 @@ class Application extends Model {
     }
 
     public function setExpert(CompanyMember $expert) {
-        if ($this->expert->id !== $expert->id) {
+        if (($this->expert->id ?? null) !== $expert->id) {
             $previousExpert = $this->expert;
             $this->update(['expert_id' => $expert->id]);
             event(new ApplicationExpertChanged($this, $previousExpert));
         }
     }
 
+    public function isExpert(?User $user = null): bool {
+        return $this->expert()->whereHas('user', function($query) use($user) {
+            $query->where(['user_id' => $user->id ?? null]);
+        })->exists();
+    }
+
     public static function generateNumber($start = 100, $digits = 5): string {
         $res = intval(static::query()->max('number') ?? $start) + 1;
         while (strlen($res) < $digits) {

app/Services/PermissionsService.php

@@ -41,7 +41,7 @@ class PermissionsService {
     }
 
     public function applicationPermissions(): array {
-        return ['edit' => $this->model->submitter_id === $this->user->id, 'reply' => $this->user->isExpert, 'manage' => $this->user->isApplicationsManager];
+        return ['edit' => $this->model->submitter_id === $this->user->id, 'reply' => $this->model->isExpert($this->user), 'manage' => $this->user->isApplicationsManager];
     }
 
     public function pagePermissions(): array {