Grid validate filtering expressions tree (#15564)

* fix(grid): add test for filtering without condition operator

* fix(grid): validate if condition exists before calling its logic function

* chore(grid): use better naming for test

* fix(grid): call codition.logic only if existing

Author: hanastasov

projects/igniteui-angular/src/lib/data-operations/filtering-strategy.spec.ts

@@ -49,6 +49,20 @@ describe('Unit testing FilteringStrategy', () => {
         const res = fs.matchRecord(rec, expressionTree);
         expect(res).toBeTruthy();
     });
+    it ('tests `findMatchByExpression` for working with filtering operands with missing condition', () => {
+        const rec = data[0];
+        const expressionTree = new FilteringExpressionsTree(FilteringLogic.Or);
+        expressionTree.filteringOperands = [
+            {
+                conditionName: 'contains',
+                fieldName: 'string',
+                ignoreCase: false,
+                searchVal: 'ROW'
+            }
+        ];
+        const res = fs.matchRecord(rec, expressionTree);
+        expect(res).toBeFalsy();
+    });
     it ('tests `findMatch`', () => {
         const rec = data[0];
         const res = fs.findMatchByExpression(rec, {

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

@@ -39,9 +39,8 @@ export interface IgxFilterItem {
 export abstract class BaseFilteringStrategy implements IFilteringStrategy  {
     // protected
     public findMatchByExpression(rec: any, expr: IFilteringExpression, isDate?: boolean, isTime?: boolean, grid?: GridType): boolean {
-        const cond = expr.condition;
         const val = this.getFieldValue(rec, expr.fieldName, isDate, isTime, grid);
-        return cond.logic(val, expr.searchVal, expr.ignoreCase);
+        return expr.condition?.logic(val, expr.searchVal, expr.ignoreCase);
     }
 
     // protected