Prevent error when ETS related websocket connection is closed
Prevent error when ETS related websocket connection is closed

Check if the called epl_tracer (dedicated to one node) is alive
when trying to disable ETS tracing on websocket connection close.

mkacper/erlangpl,erlanglab/erlangpl,erlanglab/erlangpl,mkacper/erlangpl,erlanglab/erlangpl,mkacper/erlangpl