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

Author: hanastasov

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