fix(VDataTable): avoid changing page if oldOptions is not defined

[webdevnerdstuff]

fixes #17966

Description

Fixes initial checking of old search value to include a check for undefined. Without it the condition was always true.

Markup:

<template>
  <v-text-field
    v-model="search"
    label="Search"
  />
  <v-data-table
    :headers="headers"
    :items="desserts"
    :items-per-page="5"
    :page="2"
    :search="search"
  />
</template>

<script setup lang="ts">
  import { ref } from 'vue'

  const search = ref('')

  const headers = ref([
    {
      title: 'Dessert (100g serving)',
      align: 'start',
      sortable: false,
      key: 'name',
    },
    { title: 'Calories', key: 'calories' },
    { title: 'Fat (g)', key: 'fat' },
    { title: '', key: 'data-table-expand' },
  ] as const)
  const desserts = ref([
    {
      name: 'Frozen Yogurt',
      calories: 159,
      fat: 6,
    },
    {
      name: 'KitKat',
      calories: 518,
      fat: 26,
    },
    {
      name: 'Ice cream sandwich with some really long name',
      calories: 237,
      fat: 9,
    },
    {
      name: 'Eclair',
      calories: 262,
      fat: 16,
    },
    {
      name: 'Cupcake',
      calories: 305,
      fat: 3.7,
    },
    {
      name: 'Gingerbread',
      calories: 356,
      fat: 16,
    },
    {
      name: 'Jelly bean',
      calories: 375,
      fat: 0,
    },
    {
      name: 'Honeycomb',
      calories: 408,
      fat: 3.2,
    },
    {
      name: 'Donut',
      calories: 452,
      fat: 25,
    },
    {
      name: 'KitKat',
      calories: 518,
      fat: 26,
    },
  ])
</script>

[webdevnerdstuff]

@MajesticPotatoe or @KaelWD does the Cypress test need to be updated for this change? Cypress tests are above my head.

Fail point:
line: 113
vuetify/packages/vuetify/src/components/VDataTable/tests/VDataTable.spec.cy.tsx

cy.emitted(VDataTable, 'update:page')
      .should('deep.equal', [[2], [1]])