refactor(radio-group): modify checked validity

Author: simeonoff

projects/igniteui-angular/src/lib/directives/radio/radio-group.directive.ts

@@ -435,7 +435,7 @@ export class IgxRadioGroupDirective implements AfterContentInit, ControlValueAcc
     private _selectRadioButton() {
         if (this.radioButtons) {
             this.radioButtons.forEach((button) => {
-                if (!this._value) {
+                if (this._value === null) {
                     // no value - uncheck all radio buttons
                     if (button.checked) {
                         button.checked = false;

projects/igniteui-angular/src/lib/radio/radio.component.ts

@@ -366,10 +366,6 @@ export class IgxRadioComponent implements ControlValueAccessor, EditorProvider {
     public select() {
         this.nativeRadio.nativeElement.focus();
 
-        if (this.value === undefined || this.value === '' || this.value === null) {
-            this.value = 'on';
-        }
-
         if(!this.checked) {
             this.checked = true;
             this.change.emit({ value: this.value, radio: this });