Turn on -o filenames in _tilde() only when it produces completions.

bash_completion

@@ -852,10 +852,10 @@ _tilde()
 {
     local result=0
     if [[ $1 == ~* && $1 != */* ]]; then
-        compopt -o filenames 2>/dev/null
         # Try generate ~username completions
         COMPREPLY=( $( compgen -P '~' -u "${1#\~}" ) )
         result=${#COMPREPLY[@]}
+        [ $result -gt 0 ] && compopt -o filenames 2>/dev/null
     fi
     return $result
 }