Sign companies don't always win
What's interesting here is that earlier 1st amendment cases on signs seemed to indicate that an ordinance that discriminated against types of speech or didn't effectively bridle the discretion of the administrator were void to prevent the erection of the sign. That is, if the ordinance was infirm, the local government lacked the authority to deny the permit (even on construction, size, location or other less problematic grounds). This case seems to hold that when the objectionable parts are severable, there's no automatic order to issue the permit.
That being the case, the Court found that because the City amended the ordinance to make it constitutional, AND there was no likelihood that it would go back to unconstitutional procedures or discrimination, the case was moot.