MAPG-199 fix issues found by PHPStan

src/Repository/PlaceRepository.php

@@ -46,14 +46,20 @@ class PlaceRepository
         return $place;
     }
 
-    private function selectRandomFromDbForMap(int $mapId, array $exclude): ?Place
+    private function selectRandomFromDbForMap(int $mapId, array $exclude): Place
     {
         //TODO: omit table name here
         $select = new Select(\Container::$dbConnection, 'places');
         $select->where('id', 'NOT IN', $exclude);
         $select->where('map_id', '=', $mapId);
 
-        $numberOfPlaces = $select->count(); // TODO: what if 0
+        $numberOfPlaces = $select->count();
+
+        //TODO: prevent this
+        if ($numberOfPlaces === 0) {
+            throw new \Exception('There is no selectable place (count was 0).');
+        }
+
         $randomOffset = random_int(0, $numberOfPlaces - 1);
 
         $select->orderBy('id');