Fix #9925: Industry tile layout validation for layouts of only one tile

[JGRennison]

Motivation / Problem

Fix #9925, incorrect validation of industry tile layouts which contain only one tile in #9902.

Description

Perform valid tile check separately from tile coordinate duplication check due to different loop bounds.

Limitations

N/A

Checklist for review

Some things are not automated, and forgotten often. This list is a reminder for the reviewers.

• The bug fix is important enough to be backported? (label: 'backport requested')
• This PR touches english.txt or translations? Check the guidelines
• This PR affects the save game format? (label 'savegame upgrade')
• This PR affects the GS/AI API? (label 'needs review: Script API')
  • ai_changelog.hpp, gs_changelog.hpp need updating.
  • The compatibility wrappers (compat_*.nut) need updating.
• This PR affects the NewGRF API? (label 'needs review: NewGRF')
  • newgrf_debug_data.h may need updating.
  • PR must be added to API tracker

[glx22]

The boolean is not really needed, but I think it's clearer with it.