commit 45ac9648bf1c1d1d9a75c5a6097c2a32e7c0392f
Author: Till Hofmann <thofmann@fedoraproject.org>
Date:   Sun Feb 9 13:03:52 2020 +0100

    Avoid calling strcmp on nullptr
    
    The function group_handler may get a nullptr as `new_group`. If that's
    the case, return -1, as if `new_group` was the empty string.

diff --git a/swaybar/tray/icon.c b/swaybar/tray/icon.c
index 8adefda6..c383bc63 100644
--- a/swaybar/tray/icon.c
+++ b/swaybar/tray/icon.c
@@ -89,6 +89,9 @@ static bool validate_icon_theme(struct icon_theme *theme) {
 static bool group_handler(char *old_group, char *new_group,
 		struct icon_theme *theme) {
 	if (!old_group) { // first group must be "Icon Theme"
+		if (!new_group) {
+			return -1;
+		}
 		return strcmp(new_group, "Icon Theme");
 	}