feat(filterItem): improve value handling in toJson method

Enhanced the  method in  to handle various cases for
the  property more robustly. Added checks for empty or invalid
values and adjusted mapping logic for specific filter types like
 and .

- Updated type annotations for better clarity.
- Removed unnecessary trailing commas in imports.
- Improved readability and maintainability of the code.

frontend/app/mstore/types/filterItem.ts

@@ -2,7 +2,7 @@ import { FilterCategory, FilterKey, FilterType } from 'Types/filter/filterType';
 import {
   conditionalFiltersMap,
   filtersMap,
-  mobileConditionalFiltersMap,
+  mobileConditionalFiltersMap
 } from 'Types/filter/newFilter';
 import { action, makeAutoObservable, observable } from 'mobx';
 
@@ -35,7 +35,7 @@ export default class FilterItem {
     makeAutoObservable(this);
 
     if (Array.isArray(data.filters)) {
-      data.filters = data.filters.map(function (i: Record<string, any>) {
+      data.filters = data.filters.map(function(i: Record<string, any>) {
         return new FilterItem(i);
       });
     }
@@ -132,22 +132,29 @@ export default class FilterItem {
     return this;
   }
 
-  toJson(): any {
+  toJson(): Record<string, any> {
     const isMetadata = this.category === FilterCategory.METADATA;
-    const json = {
+    const json: Record<string, any> = {
       type: isMetadata ? FilterKey.METADATA : this.key,
       isEvent: Boolean(this.isEvent),
-      value: this.value.map((i: any) => i ? i.toString() : ''),
       operator: this.operator,
       source: isMetadata ? this.key.replace(/^_/, '') : this.source,
       sourceOperator: this.sourceOperator,
       filters: Array.isArray(this.filters)
         ? this.filters.map((i) => i.toJson())
-        : [],
+        : []
     };
-    if (this.type === FilterKey.DURATION) {
+
+    if (!this.value || !Array.isArray(this.value) || this.value.length === 0 || this.value[0] === '') {
+      json.value = [];
+    } else if (this.type === FilterKey.DURATION) {
       json.value = this.value.map((i: any) => (!i ? 0 : i));
+    } else if (this.type === FilterKey.FETCH_DURATION) {
+      json.value = this.value.map((i: any) => (!i ? 0 : String(i)));
+    } else {
+      json.value = this.value.map((i: any) => i ? String(i) : '');
     }
+
     return json;
   }
 }