[BUGFIX] Fix possible regression in cObjGet()

With #99503 `cObjGet()` was implemented as a wrapper around
the strictly typed cObjGetSeparated method, effectively
enforcing the first argument to be an array, while
previously non array values were returned as an empty string.

Resolves: #102328
Related: #99503
Releases: main, 12.4, 11.5
Change-Id: I7c04307f14da5a93e12672b36de163071dad7359
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/81662


Tested-by: core-ci <typo3@b13.com>
Tested-by: Benjamin Franzke <ben@bnf.dev>
Reviewed-by: Benjamin Franzke <ben@bnf.dev>