quote: Fix returning out of string pointer, take 2
quote: Fix returning out of string pointer, take 2

In commit a45febd767 only part of problem has been covered.
Need to be ready for strings like

 | `a

http://bugzilla.nasm.us/show_bug.cgi?id=3392295

Reported-by: Hanno Boeck <898dba66b7f38fdb797b262b137097fc973d6485@hboeck.de>
Signed-off-by: Cyrill Gorcunov <7a1ea01eee6961eb1e372e3508c2670446d086f4@gmail.com>

techkey/nasm,techkey/nasm,techkey/nasm,techkey/nasm,techkey/nasm