submodule::module_clone(): silence die() message from module_name()

The die() message that may occur in module_name() is not really relevant
to the user when called from module_clone(); the latter handles the
"failure" (no submodule mapping) anyway.

Analysis of other callsites is left to future work.

Acked-by: Jens Lehmann <Jens.Lehmann@web.de>
Signed-off-by: Tay Ray Chuan <rctay89@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

git-submodule.sh

@@ -124,7 +124,7 @@ module_clone()
 	reference="$3"
 	gitdir=
 	gitdir_base=
-	name=$(module_name "$path")
+	name=$(module_name "$path" 2>/dev/null)
 	base_path=$(dirname "$path")
 
 	gitdir=$(git rev-parse --git-dir)