优化

Former-commit-id: d7ec4318281d4b79055e97ffa69972021a271829

src/main/java/xyz/wbsite/dbtool/javafx/JavaFxApplication.java

@@ -974,6 +974,8 @@ public class JavaFxApplication extends Application {
                         String fieldType = (String) event.getNewValue();
                         field.setFieldLength(FieldType.parse(fieldType).getDefaultLength());
                         field.setFieldType(fieldType);
+                        field.getSelectItems().clear();
+                        field.getDictItems().clear();
                         mFields.refresh();
                     }
                 });