Fix getConnectionCount() call crashing if called before begin()

src/WebSerial.cpp

@@ -115,7 +115,7 @@ void WebSerialClass::onMessage(WSLStringMessageHandler callback) {
 }
 
 bool WebSerialClass::getConnectionCount() {
-  return _ws->count();
+  return _ws == nullptr ? 0 : _ws->count();
 }
 
 // Print func
@@ -315,4 +315,4 @@ size_t WebSerialClass::_write_row_packet(uint8_t* dest, const uint8_t *payload,
   return WSL_HEAD_LEN + WSL_MSG_SIZE_LEN + payload_size;
 }
 
-WebSerialClass WebSerial;
+WebSerialClass WebSerial;