bugfix: make sure collage limit is always defined

Change-Id: I19c98a06a67c8746a0efddcd7a8e449e50e051fa

Author: andi34

api/admin.php

@@ -255,6 +255,7 @@
     }
 
     // Collage json config
+    $newConfig['collage']['limit'] = $newConfig['collage']['limit'] ?? $defaultConfig['collage']['limit'];
     if ($newConfig['collage']['enabled']) {
         $collageConfigFilePath = Collage::getCollageConfigPath($newConfig['collage']['layout'], $newConfig['collage']['orientation']);
 
@@ -307,6 +308,7 @@
         }
         if ($newConfig['collage']['limit'] < 1) {
             $newConfig['collage']['enabled'] = false;
+            $newConfig['collage']['limit'] = $defaultConfig['collage']['limit'];
             $logger->debug('Invalid collage limit, must be 1 or greater. Collage disabled.');
         }
     }

src/Configuration/Section/CollageConfiguration.php

@@ -49,6 +49,15 @@ public static function getNode(): NodeDefinition
                         })
                         ->end()
                     ->end()
+                ->integerNode('limit')
+                    ->defaultValue(4)
+                    ->min(1)
+                    ->max(999)
+                    ->beforeNormalization()
+                        ->ifString()
+                        ->then(function (string $value): int { return intval($value); })
+                        ->end()
+                    ->end()
                 ->scalarNode('dashedline_color')->defaultValue('#000000')->end()
                 ->booleanNode('keep_single_images')->defaultValue(false)->end()
                 ->scalarNode('key')