--- a/mercurial/templatefuncs.py	Sat Feb 24 19:56:59 2018 -0500
+++ b/mercurial/templatefuncs.py	Sat Mar 31 10:13:42 2018 -0400
@@ -184,7 +184,7 @@
         data = repo.wvfs.tryread('.mailmap')
         cache['mailmap'] = stringutil.parsemailmap(data)
 
-    return stringutil.mapname(cache['mailmap'], author) or author
+    return stringutil.mapname(cache['mailmap'], author)
 
 @templatefunc('pad(text, width[, fillchar=\' \'[, left=False]])',
               argspec='text width fillchar left')