aa-mergeprof: act() mergeprofiles.clear_common() call crashes

aa-mergeprof around line 120:

def act(files, merge_mode, merging_profile):
    mergeprofiles = Merge(files)
    #Get rid of common/superfluous stuff
    mergeprofiles.clear_common()

crashes with

 Traceback (most recent call last):
   File "/home/cb/apparmor/HEAD-CLEAN/utils/aa-mergeprof", line 764, in <module>
     main()
   File "/home/cb/apparmor/HEAD-CLEAN/utils/aa-mergeprof", line 114, in main
     act([user_file, base_file, None], 2, profile_name)
   File "/home/cb/apparmor/HEAD-CLEAN/utils/aa-mergeprof", line 123, in act
     mergeprofiles.clear_common()
   File "/home/cb/apparmor/HEAD-CLEAN/utils/aa-mergeprof", line 191, in clear_common
     deleted += user_base.compare_profiles()
   File "/home/cb/apparmor/HEAD-CLEAN/utils/apparmor/cleanprofile.py", line 42, in compare_profiles
     deleted += self.remove_duplicate_rules(profile)
   File "/home/cb/apparmor/HEAD-CLEAN/utils/apparmor/cleanprofile.py", line 72, in remove_duplicate_rules
     deleted += delete_path_duplicates(self.profile.aa[program][hat], self.other.aa[program][hat], 'allow', self.same_file)
   File "/home/cb/apparmor/HEAD-CLEAN/utils/apparmor/cleanprofile.py", line 107, in delete_path_duplicates
     profile_other[allow]['path'].pop(entry)
 KeyError: '/etc/postfix/ssl/certs/mail.pem'

As a workaround, I temporarily disabled the mergeprofiles.clear_common() call.