fix bug on create mahasiswa before creating thesis class

app/Http/Controllers/Auth/RegisterController.php

@@ -109,7 +109,16 @@ class RegisterController extends Controller
                 Dosen::create(['id'=>$user->id]);
             } else if ($role == User::ROLE_MAHASISWA) {
                 $id_kelas_tesis = KelasTesis::orderByRaw('updated_at - created_at DESC')->first();
-                Mahasiswa::create(['id'=>$user->id, 'id_kelas_tesis'=>$id_kelas_tesis->id]);
+                if ($id_kelas_tesis == NULL) {
+                    $user->delete();
+                    echo '<div class="alert alert-warning alert-dismissible fade show text-center">
+                            <button type="button" class="close" data-dismiss="alert">&times;</button>
+                            Please create <strong>Kelas Tesis</strong> first.
+                         </div>';
+                    return view('auth.register');
+                } else {
+                    Mahasiswa::create(['id'=>$user->id, 'id_kelas_tesis'=>$id_kelas_tesis->id]);
+                }
             } else if ($role == User::ROLE_MANAJER) {
                 Manajer::create(['id'=>$user->id]);
             }