Bug 891551 - Part 3: Fix bug where we weren't performing a null check in dtor for NrSocket (see also bug 987380). r=bwc

media/mtransport/nr_socket_prsock.h

@@ -127,7 +127,8 @@ class NrSocket : public NrSocketBase,
 public:
   NrSocket() : fd_(nullptr) {}
   virtual ~NrSocket() {
-    PR_Close(fd_);
+    if (fd_)
+      PR_Close(fd_);
   }
 
   // Implement nsASocket