Always allocate returned mapset (so that it can be freed)

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@40210 15284696-431f-4ddb-bdfa-cd5b030d7da7

lib/gis/find_file.c

@@ -88,7 +88,7 @@ static const char *find_file(
 		G_warning(_("Using <%s@%s>"),
 			  pname, pselmapset);
 	    
-	    return pselmapset;
+	    return G_store(pselmapset);
 	}
     }
     /*