fix(测试跟踪): 创建用例，富文本框字段不填显示为null

--bug=1024542 --user=陈建星 【测试跟踪】新建、复制用例-文本框为空显示为null https://www.tapd.cn/55049933/s/1351756

framework/sdk-parent/frontend/src/utils/custom_field.js

@@ -80,7 +80,7 @@ export function parseCustomField(data, template, rules, oldFields) {
         let customField = data.fields[i];
         if (customField.id === item.id) {
           try {
-            if (item.type === "textarea" || item.type === "richText") {
+            if (item.type === "richText") {
               setDefaultValue(item, "\"" + customField.textValue + "\"");
             } else {
               setDefaultValue(item, customField.value);

test-track/frontend/src/business/case/components/BaseEditItemComponent.vue

@@ -294,12 +294,8 @@ export default {
         }
       }
 
-      if (
-        this.contentObject.content.type === "input" ||
-        this.contentObject.content.type === "richText"
-      ) {
-        if (this.contentObject.content.defaultValue === "" ||
-          this.contentObject.content.defaultValue == null) {
+      if (['input', 'richText', 'textarea'].indexOf(this.contentObject.content.type) > -1) {
+        if (!this.contentObject.content.defaultValue) {
           this.isCustomNone = true;
           return this.$t("case.none");
         } else {
@@ -308,8 +304,7 @@ export default {
         }
       }
 
-      if (this.contentObject.content.defaultValue === "" ||
-        this.contentObject.content.defaultValue == null) {
+      if (!this.contentObject.content.defaultValue) {
         this.isCustomNone = true;
         return this.$t("case.none");
       } else {