configurationmanager: fix nullptr access

This patch fixes a nullptr access to non checked pointer
returned by ring::Manager::instance().getCurrentCall().
This is a bug introduced by commit 3939750f

Refs #77483

Change-Id: I8bd1b67a8bb97c4afc86609e9fe276797bf54aa2

src/client/configurationmanager.cpp

@@ -414,7 +414,7 @@ setCodecDetails(const std::string& accountID,
             if (foundCodec->isRunning) {
                 RING_WARN("%s running. Need to restart encoding",
                         foundCodec->systemCodecInfo.name.c_str());
-                auto call = ring::Manager::instance().getCurrentCall();
+                if (auto call = ring::Manager::instance().getCurrentCall())
                     call->restartMediaSender();
             }
             ring::emitSignal<ConfigurationSignal::MediaParametersChanged>(accountID);