Right-clicking when the bucket tool is enabled means "erase all instances of this tile".
So it doesn't make sense to try doing this for empty tiles :P
Fixes#10065
(cherry picked from commit 95da12212b)
The other subfolders of tools/ had already been moved to either
editor/, misc/ or thirdparty/, so the hiding the editor code that
deep was no longer meaningful.
(Manual redo of 49c065d29c)