Notice: Undefined index: suppress_filters

If $query->query_vars['suppress_filters'] is not set you will get that message.

Use empty($query->query_vars['suppress_filters']) instead of false == $query->query_vars['suppress_filters'] ) or use $query->get('suppress_filters') like this false == $query->get('suppress_filters').

Untested (minimally tested) but I believe either of those should give you the same results minus the notice.