fix compile with -Werror

--- src/tools/asm/cmdlib.c.orig	Sat Jul 25 13:22:03 2015
+++ src/tools/asm/cmdlib.c	Sat Jul 25 13:22:31 2015
@@ -313,7 +313,7 @@
 char *ExpandPath (const char *path)
 {
 	static char full[1024];
-	if (!qdir)
+	if (!qdir[0])
 		Error ("ExpandPath called without qdir set");
 	if (path[0] == '/' || path[0] == '\\' || path[1] == ':') {
 		strcpy( full, path );
@@ -326,7 +326,7 @@
 char *ExpandGamePath (const char *path)
 {
 	static char full[1024];
-	if (!qdir)
+	if (!qdir[0])
 		Error ("ExpandGamePath called without qdir set");
 	if (path[0] == '/' || path[0] == '\\' || path[1] == ':') {
 		strcpy( full, path );