convert a couple uses of strlen() to use ast_strlen_zero()

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@13621 65c4cc65-6c06-0410-ace0-fbb531ad65f3

image.c

@@ -97,12 +97,12 @@ static int file_exists(char *filename)
 static void make_filename(char *buf, int len, char *filename, const char *preflang, char *ext)
 {
 	if (filename[0] == '/') {
-		if (preflang && strlen(preflang))
+		if (!ast_strlen_zero(preflang))
 			snprintf(buf, len, "%s-%s.%s", filename, preflang, ext);
 		else
 			snprintf(buf, len, "%s.%s", filename, ext);
 	} else {
-		if (preflang && strlen(preflang))
+		if (!ast_strlen_zero(preflang))
 			snprintf(buf, len, "%s/%s/%s-%s.%s", ast_config_AST_VAR_DIR, "images", filename, preflang, ext);
 		else
 			snprintf(buf, len, "%s/%s/%s.%s", ast_config_AST_VAR_DIR, "images", filename, ext);