most FREE_SET_NULL replaced with free

FREE_SET_NULL makes extra assignment of NULL for pointers in stack or
dynamic memory that is going to be freed.
FREE_SET_NULL is useful for pointers that can be used in future.

src/ui/console.c

@@ -784,7 +784,7 @@ cons_show_room_invite(const char * const invitor, const char * const room,
         notify_invite(display_from, room, reason);
     }
 
-    FREE_SET_NULL(display_from);
+    free(display_from);
 
     ui_console_dirty();
     cons_alert();

src/ui/core.c

@@ -293,8 +293,9 @@ ui_incoming_msg(const char * const from, const char * const message,
     GTimeVal *tv_stamp, gboolean priv)
 {
     gboolean win_created = FALSE;
-    char *display_from;
+    char *display_from = NULL;
     win_type_t win_type;
+
     if (priv) {
         win_type = WIN_PRIVATE;
         display_from = get_nick_from_full_jid(from);
@@ -436,7 +437,7 @@ ui_incoming_msg(const char * const from, const char * const message,
     if (prefs_get_boolean(PREF_NOTIFY_MESSAGE))
         notify_message(display_from, ui_index);
 
-    FREE_SET_NULL(display_from);
+    free(display_from);
 }
 
 void