Merge pull request baidu#10245 from 2betop/fix-combo-defaultvalue

fix: 修复 combo 中通过 visibleOn 新出来的字段默认值没有起作用的问题 Close: baidu#9947

packages/amis-core/src/renderers/Form.tsx

@@ -1051,7 +1051,7 @@ export default class Form extends React.Component<FormProps, object> {
       return;
     }
     store.changeValue(name, value, changePristine);
-    if (!changePristine) {
+    if (!changePristine || typeof value !== 'undefined') {
       (formLazyChange === false ? this.emitChange : this.lazyEmitChange)(
         submit
       );