prevent a crash if im::sendSipMessage fails

im::sendSipMessage() may throw an exception but caller
doesn't take that into account. This may cause undefined behaviour,
like a crash on some platforms.

This patch encapsulates the im::sendSipMessage() call into a try/catch.

Change-Id: Ie07105f02d64a37a009e510bb674716ec20212c9
Tuleap: #1172

src/sip/sipcall.cpp

@@ -671,7 +671,9 @@ SIPCall::sendTextMessage(const std::map<std::string, std::string>& messages,
             c->sendTextMessage(messages, from);
     } else {
         if (inv) {
+            try {
                 im::sendSipMessage(inv.get(), messages);
+            } catch (...) {}
         } else {
             pendingOutMessages_.emplace_back(messages, from);
             RING_ERR("[call:%s] sendTextMessage: no invite session for this call", getCallId().c_str());