fix(time-picker): isSelectedTIme condition for fr seconds

Author: ddaribo

Diff for: projects/igniteui-angular/src/lib/time-picker/time-picker.directives.ts

@@ -280,7 +280,7 @@ export class IgxTimeItemDirective {
                 const fractionalSecondsPart = inputDateParts.find(element => element.type === 'fractionalSeconds');
                 const partValue = DateTimeUtil.getPartValue(this.timePicker.selectedDate, fractionalSecondsPart, fractionalSecondsPart.format.length);
                 const leadingZerosRegex = /^0+/;
-                return partValue.replace(leadingZerosRegex, '') === currentValue.replace(leadingZerosRegex, '');
+                return this.value !== '' && partValue.replace(leadingZerosRegex, '') === currentValue.replace(leadingZerosRegex, '');
             case 'ampmList':
                 const ampmPart = inputDateParts.find(element => element.format.indexOf('a') !== -1 || element.format === 'tt');
                 return DateTimeUtil.getPartValue(this.timePicker.selectedDate, ampmPart, ampmPart.format.length) === this.value;