test: ignore a failure to send a pong

Our automatic pong handler unconditionally sends a Pong back to the EIS
implementation. For some tests and depending on timing we may have
been disconnected already, resulting in a BrokenPipeError that fails
us the test. Ignore that error.

Part-of: <https://gitlab.freedesktop.org/libinput/libei/-/merge_requests/317>

test/test_protocol.py

@@ -287,7 +287,10 @@ class Ei:
                 # Automatic ping/pong handler
                 def ping(conn, id, version, new_objects={}):
                     pingpong = new_objects["ping"]
-                    ei.send(pingpong.Done(0))
+                    try:
+                        ei.send(pingpong.Done(0))
+                    except BrokenPipeError:
+                        pass
 
                 ei.connection.connect("Ping", ping)