Fix critical errors

src/Database.php

@@ -13,6 +13,7 @@
 use InvalidArgumentException;
 use PDO;
 use PDOStatement;
+use RuntimeException;
 use SimpleCrud\Fields\Boolean;
 use SimpleCrud\Fields\Date;
 use SimpleCrud\Fields\Datetime;
@@ -219,7 +220,7 @@ public function executeTransaction(callable $callable)
                 $this->commit();
             }
         } catch (Exception $exception) {
-            if ($transaction) {
+            if (isset($transaction) && $transaction) {
                 $this->rollBack();
             }
 

src/EventDispatcher/Dispatcher.php

@@ -4,6 +4,7 @@
 namespace SimpleCrud\EventDispatcher;
 
 use Psr\EventDispatcher\EventDispatcherInterface;
+use Psr\EventDispatcher\ListenerProviderInterface;
 
 class Dispatcher implements EventDispatcherInterface
 {

src/Fields/Serializable.php

@@ -23,7 +23,7 @@ public function format($value)
         return @unserialize($value, $this->config['unserialize']) ?: [];
     }
 
-    protected function formatToDatabase($value): string
+    protected function formatToDatabase($value): ?string
     {
         if ($value === null) {
             return $value;

src/Queries/SelectAggregate.php

@@ -26,7 +26,7 @@ public function __construct(Table $table, string $function, string $field = 'id'
         $function = strtoupper($function);
 
         if (!in_array($function, self::AGGREGATION_FUNCTIONS)) {
-            throw InvalidArgumentException(
+            throw new InvalidArgumentException(
                 sprintf('Invalid aggregation function. Must be one of the followings: %s', implode(', ', self::AGGREGATION_FUNCTIONS))
             );
         }

src/Queries/Traits/HasRelatedWith.php

@@ -12,8 +12,7 @@
 trait HasRelatedWith
 {
     /**
-     * @param Row|RowCollection|Table
-     * @param mixed $related
+     * @param Row|RowCollection|Table $related
      */
     public function relatedWith($related): self
     {