fix(VDatePicker): using the start range that has been cleared

[TIM56887]

Description

fixes #19854
Added a condition to reset the rangeStart.value to undefined when the model's value array is empty

Markup:

<template>
  <v-container>
    <v-row justify="space-around">
      <v-date-picker v-model="date" multiple="range"></v-date-picker>
    </v-row>
    <v-row justify="space-around">
      <v-btn @click="clearDate">Clear</v-btn>
    </v-row>
  </v-container>
</template>

<script setup>
  import { ref } from 'vue'

  const date = ref([])

  const clearDate = () => {
    date.value = []
  }
</script>