Fix uPnP invalid memory access when destroying the context

[linphone] / mediastreamer2

diff --git a/mediastreamer2 b/mediastreamer2
index a8538b58b7845f06f8526aca9bcf6657cf0abea5..841c656e8804d216e2aa28a170fe1473ae3f4732 160000 (submodule)
--- a/mediastreamer2
+++ b/mediastreamer2
@@ -1 +1 @@
-Subproject commit a8538b58b7845f06f8526aca9bcf6657cf0abea5
+Subproject commit 841c656e8804d216e2aa28a170fe1473ae3f4732