[PHPStan] Resolved phpstan issues (#79)

Author: mikadamczyk

src/bundle/Command/MigrateLegacyMatrixCommand.php

@@ -98,7 +98,7 @@ public function execute(InputInterface $input, OutputInterface $output): int
             }
 
             if ($isValidXml) {
-                $columnList = $xml->xpath('//column-name');
+                $columnList = $xml->xpath('//column-name') ?: [];
 
                 $columns = [];
 
@@ -178,7 +178,8 @@ public function execute(InputInterface $input, OutputInterface $output): int
                         ],
                     ]);
 
-                    $rows = $this->convertCellsToRows($xml->xpath('c'), $columns);
+                    $cells = $xml->xpath('c') ?: [];
+                    $rows = $this->convertCellsToRows($cells, $columns);
 
                     $fieldValue->data['entries'] = $rows;
 

src/lib/FieldType/Mapper/MatrixFormMapper.php

@@ -61,7 +61,7 @@ public function mapFieldDefinitionForm(FormInterface $fieldDefinitionForm, Field
      */
     public function mapFieldValueForm(FormInterface $fieldForm, FieldData $data): void
     {
-        $fieldDefinition = $data->fieldDefinition;
+        $fieldDefinition = $data->getFieldDefinition();
         $fieldSettings = $fieldDefinition->getFieldSettings();
         $formConfig = $fieldForm->getConfig();