[BUGFIX] Prevent TypeError in DatabaseIntegrityController

In advanced query the operator "is in list" makes value
be an array. Then switch the field to a non-array field
type, and you get the following TypeError:

```
  htmlspecialchars(): Argument #1 ($string) must be of type
  string, array given.
```

This resets the array value to an empty string.

Resolves: #103487
Releases: main, 12.4, 11.5
Change-Id: Ifc6ef7e90d49a05ecb4b6d4869eea13c151b1b2a
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/84198


Tested-by: Stefan Bürk <stefan@buerk.tech>
Reviewed-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: core-ci <typo3@b13.com>