ModelChange的text_diff判空并赋值空字符串

app/Services/History/ModelChangeDetector.php

@@ -32,7 +32,7 @@ class ModelChangeDetector
                 'old' => is_array($model->getOriginal($field)) ? json_encode($model->getOriginal($field)) : $model->getOriginal($field),
                 'field' => $field,
                 'new' => is_array($model->$field) ? json_encode($model->$field) : $model->$field,
-                'diff' => in_array($field, $diffFields) ? text_diff($model->getOriginal($field), $model->$field) : null,
+                'diff' => in_array($field, $diffFields) ? text_diff($model->getOriginal($field) ?? '', $model->$field ?? '') : null,
             ];
         }