Don't try to set default_val in volume_limit_is_changed().

We don't use the default_val anywhere, so there's no need to try
to use it in a buggy and null pointer dereferencing way here.

Change-Id: Ie60dbab7647056e2bf457cb5dcc5b60012ea1651
diff --git a/apps/settings_list.c b/apps/settings_list.c
index 01bc5c5..838d783 100644
--- a/apps/settings_list.c
+++ b/apps/settings_list.c
@@ -675,10 +675,8 @@
 }
 static bool volume_limit_is_changed(void* setting, void* defaultval)
 {
+    (void)defaultval;
     int current = *(int*)setting;
-
-    if ((int*)defaultval == NULL)
-        *(int*)defaultval = sound_max(SOUND_VOLUME);
     return (current != sound_max(SOUND_VOLUME));
 }
 static void volume_limit_set_default(void* setting, void* defaultval)