Fix erroneous widget lookup after a widget in the glade file has been renamed

This is a result of the glorious idea of glade to have all widget names
in one file have unique names, but not verifying that we really can
continue to do the lookup as before. Oh well.

git-svn-id: svn+ssh://svn.gnucash.org/repo/gnucash/trunk@22817 57a11ea4-9604-0410-9ed3-97b8803252fd