File with empty mapping should not show empty records

[chavda-bhavik]

Describe the bug Impler validates empty files at first. But none of the columns are required, and the user doesn't do any mapping. The review step shows a table with empty records.

To Reproduce Steps to reproduce the behavior:

1. Go to https://web.impler.io
2. Create Import with following schema,

[
  {
    "key": "Email",
    "name": "Email",
    "type": "Email",
    "alternateKeys": [],
    "isRequired": false,
    "isUnique": false,
    "isFrozen": false,
    "dateFormats": [
      "DD/MM/YYYY"
    ],
    "selectValues": []
  },
  {
    "key": "First Name",
    "name": "First Name",
    "type": "String",
    "alternateKeys": [],
    "isRequired": false,
    "isUnique": false,
    "isFrozen": false,
    "dateFormats": [
      "DD/MM/YYYY"
    ],
    "selectValues": []
  },
  {
    "key": "Last Name",
    "name": "Last Name",
    "type": "String",
    "alternateKeys": [],
    "isRequired": false,
    "isUnique": false,
    "isFrozen": false,
    "dateFormats": [
      "DD/MM/YYYY"
    ],
    "selectValues": []
  },
  {
    "key": "Company Name",
    "name": "Company Name",
    "type": "String",
    "alternateKeys": [],
    "isRequired": false,
    "isUnique": false,
    "isFrozen": false,
    "dateFormats": [
      "DD/MM/YYYY"
    ],
    "selectValues": []
  },
  {
    "key": "Twitter Handle",
    "name": "Twitter Handle",
    "type": "String",
    "alternateKeys": [],
    "isRequired": false,
    "isUnique": false,
    "isFrozen": false,
    "dateFormats": [
      "DD/MM/YYYY"
    ],
    "selectValues": []
  },
  {
    "key": "LinkedIn Handle",
    "name": "LinkedIn Handle",
    "type": "String",
    "alternateKeys": [],
    "isRequired": false,
    "isUnique": false,
    "isFrozen": false,
    "dateFormats": [
      "DD/MM/YYYY"
    ],
    "selectValues": []
  },
  {
    "key": "Lead Status",
    "name": "Lead Status",
    "type": "String",
    "alternateKeys": [],
    "isRequired": false,
    "isUnique": false,
    "isFrozen": false,
    "dateFormats": [
      "DD/MM/YYYY"
    ],
    "selectValues": []
  }
]

3. Import data with the following file. Ma Contacts (sample).xlsx
4. Do not map any columns.
5. The review step will show empty records,

Expected behavior The review step should exclude these empty records.

Additional context We can add check here for empty records, https://github.com/implerhq/impler.io/blob/next/apps/api/src/app/review/usecases/do-review/base-review.usecase.ts#L335