[BUGFIX] Suggest wizard doesn't work in page flexforms

When using the suggest wizard from within a flexform in a page it
doesn't work properly. The $row variable was only set when processing
tables other than pages but is required for proper flexform handling.

Change-Id: I0eec29b3c7266bae809e2753cdee726a4c50b1ab
Resolves: #59642
Releases: 6.3, 6.2, 6.1
Reviewed-on: https://review.typo3.org/31422
Reviewed-by: Markus Klein
Tested-by: Markus Klein