Fix issue with message grouping

More specifically, fixed the feature only checking as many characters as the last message had

Author: MrAlaux

CHANGELOG.md

@@ -10,4 +10,5 @@
 
 ## Bug Fixes
 
-None.
+- Message grouping only checking as many characters as the last message had,
+  causing incorrect grouping (e.g. new message "TEST" being grouped with last message "TES")

src/st_widgets.c

@@ -189,6 +189,7 @@ static void AddMessage(char *const string, int duration, const boolean is_chat_m
     static int num_copies = 0;
 
     if (hud_msg_group && message_list_tail && num_copies < MAX_COPIES
+        && strlen(string) == message_list_tail->orig_length
         && !strncmp(string, message_list_tail->string, message_list_tail->orig_length))
     {
         num_copies++;