chore(*): Applied review suggestions

Author: Otixa

projects/igniteui-angular/src/lib/data-operations/filtering-expression.interface.ts

@@ -16,7 +16,7 @@ export declare interface IFilteringExpression {
     fieldName: string;
     condition?: IFilteringOperation | null;
     conditionName?: string | null;
-    searchVal?: any | null;
+    searchVal?: any;
     searchTree?: IExpressionTree | null;
     ignoreCase?: boolean;
 }

projects/igniteui-angular/src/lib/data-operations/filtering-expressions-tree.ts

@@ -13,7 +13,7 @@ export declare interface IExpressionTree {
     operator: FilteringLogic;
     fieldName?: string | null;
     entity?: string | null;
-    returnFields?: (string | null)[];
+    returnFields?: (string | null)[] | null;
 }
 
 /* marshalByValue */

projects/igniteui-angular/src/lib/grids/grid-base.directive.ts

@@ -1856,7 +1856,7 @@ export abstract class IgxGridBaseDirective implements GridType,
             }
 
             value.type = FilteringExpressionsTreeType.Regular;
-            if (value && this._columns && this._columns.length > 0) {
+            if (value && this._columns?.length > 0) {
                 this._filteringExpressionsTree = recreateTreeFromFields(value, this._columns) as IFilteringExpressionsTree;
             } else {
                 this._filteringExpressionsTree = value;