automount crash with SIGSEGV on mount_subtree for share with blank+dash

Issue

• automount process crash with this stack :

  <Month> <Date> <Time> <hostname> systemd-coredump[4489]: Process 4441 (automount) of user 0 Stack trace of thread 4488:
              #0  0x00007f9cbce8c691 __strlen_sse2_pminub (libc.so.6)
              #1  0x00007f9cb8e629b0 mount_subtree (parse_sun.so)
              #2  0x00007f9cb8e639ed parse_mount (parse_sun.so)
              #3  0x00007f9cb3dd77ec do_parse_mount (lookup_hosts.so)
              #4  0x000055906a79afbd do_lookup_mount (automount)
              #5  0x000055906a79bad3 lookup_nss_mount (automount)
              #6  0x000055906a794674 do_mount_direct (automount)
              #7  0x00007f9cbe1eaea5 start_thread (libpthread.so.0)
              #8  0x00007f9cbce1b8dd __clone (libc.so.6)