Avoid potentially unset variable in get_fname.c

docs/CHANGES.txt

@@ -6,7 +6,7 @@ Copyright (c) 2002-2024
 Various contributors (see below, and AUTHORS.txt)
 https://tuxpaint.org/
 
-2024.October.19 (0.9.34)
+2024.October.20 (0.9.34)
   * New Magic Tools:
     ----------------
     * "Comic Dots", draws repeating dots (using a multiply blend)

src/get_fname.c

@@ -1,7 +1,7 @@
 /*
   get_fname.c
 
-  Copyright (c) 2009 - 2022
+  Copyright (c) 2009 - 2024
   https://tuxpaint.org/
 
   This program is free software; you can redistribute it and/or modify
@@ -19,7 +19,7 @@
   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
   (See COPYING.txt)
 
-  Last updated: December 11, 2022
+  Last updated: October 20, 2024
 
   $Id$
 */
@@ -104,6 +104,11 @@ char *get_fname(const char *const name, int kind)
   {
     dir = exportdir;
   }
+  else
+  {
+    /* Last resort! */
+    dir = "";
+  }
 
   snprintf(f, sizeof(f), "%s%c%s", dir, (*name) ? '/' : '\0',   /* Some mkdir()'s don't like trailing slashes */
            name);