Angular: Empty input condition for string validation not working

The following functions are defined in an Angular component:

    handleInput(event) {
        // Validate the input
        if (event.target.value.length >= 8) {
            this.validate(event.target.value);
        }
    }
    // Validation logic for provider NG_VALIDATORS will
    // Logic for NG_VALIDATORS provider, returns validation result to parent form
    /** @internal */
    validate(control) {
        const value = control.value || control;
        if (this.required && value.replace(/s+/g, '').length === 0) {
            this.hasError = this.control.touched || this.control.dirty;
            this.errorText = [{ message: this.requiredErrorMessage }];
            return this.required ? { required: 'date required' } : null;
        }
        if (!value) {
            this.hasError = false;
            return null;
        }
        const [day, month, year] = value.split('.').map(Number);
        if (day && month && year && value.length === 10) {
            const date = new Date(year, month - 1, day);
            const isDateValid = !isNaN(date.getTime()) && date.getFullYear() === year && date.getMonth() + 1 === month && date.getDate() === day;
            this.hasError = !isDateValid || date > this.maxDate || date < this.minDate;
            if (this.hasError) {
                this.hasError = true;
                this.errorText = [{ message: this.validationErrorMessage }];
                return { invalid: 'date invalid' };
            }
        }
        this.hasError = false;
        return null;
    }

This is the corresponding custom input field:

    <input
      #input
      type="text"
      mask="00.00.0000"
      autocomplete="off"
      (input)="handleInput($event)"
      [(ngModel)]="value"
    />

The input field will add with ngx-mask a mask for a date field in DD.MM.YYYY format.

Problem:

When the component is rendered, the following error is thrown:

ERROR TypeError: value.split is not a function

For this line of code: const [day, month, year] = value.split('.').map(Number);

I already tried to fix it with

if (!value) {
            this.hasError = false;
            return null;
        }

The error is shown when the component is rendered of if a string was entered in the input field and then the input has been deleted (empty input field).