The value param to the setParam() and setUriParam() of an Address is no optional.

src/address/address.h

@@ -88,12 +88,12 @@ public:
 
 	bool hasParam (const std::string &paramName) const;
 	const std::string &getParamValue (const std::string &paramName) const;
-	bool setParam (const std::string &paramName, const std::string &paramValue);
+	bool setParam (const std::string &paramName, const std::string &paramValue = "");
 	bool setParams (const std::string &params);
 
 	bool hasUriParam (const std::string &uriParamName) const;
 	const std::string &getUriParamValue (const std::string &uriParamName) const;
-	bool setUriParam (const std::string &uriParamName, const std::string &uriParamValue);
+	bool setUriParam (const std::string &uriParamName, const std::string &uriParamValue = "");
 	bool setUriParams (const std::string &uriParams);
 
 private:

src/chat/client-group-chat-room.cpp

@@ -72,7 +72,7 @@ void ClientGroupChatRoom::addParticipants (const list<Address> &addresses, const
 		session->configure(LinphoneCallOutgoing, nullptr, nullptr, me->getAddress(), focus->getAddress());
 		session->initiateOutgoing();
 		Address addr = me->getAddress();
-		addr.setParam("text", "");
+		addr.setParam("text");
 		session->getPrivate()->getOp()->set_contact_address(addr.getPrivate()->getInternalAddress());
 		session->startInvite(nullptr, subject);
 		d->setState(ChatRoom::State::CreationPending);