[gnome-music] meson: Add fallback in case XDG_DATA_DIRS is not set

[Marinus Schraal <mschraal src gnome org>]

commit c1adaaa75f9fbf3b8c3b0384bbcf1b961c9ee704
Author: Benoît Legat <benoit legat gmail com>
Date:   Tue Feb 27 10:07:31 2018 +0100

    meson: Add fallback in case XDG_DATA_DIRS is not set

 gnome-music.in | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/gnome-music.in b/gnome-music.in
index 6a379bd..04e7ee5 100755
--- a/gnome-music.in
+++ b/gnome-music.in
@@ -40,7 +40,7 @@ _LOCAL = @local_build@
 
 # In the local use case the installed schemas go in <builddir>/data
 if _LOCAL:
-    os.environ["XDG_DATA_DIRS"] = '@schemasdir@:' + os.environ["XDG_DATA_DIRS"]
+    os.environ["XDG_DATA_DIRS"] = '@schemasdir@:' + os.environ.get("XDG_DATA_DIRS", "")
 
 import gi