The channel buffer can be NULL if the proxy is disconnected, so check
for this before releasing it.

diff --git a/dlls/ole32/oleproxy.c b/dlls/ole32/oleproxy.c
index 5255474..67d89e7 100644
--- a/dlls/ole32/oleproxy.c
+++ b/dlls/ole32/oleproxy.c
@@ -346,7 +346,7 @@
         ref = InterlockedDecrement(&This->ref);
 
     if (!ref) {
-      	IRpcChannelBuffer_Release(This->chanbuf);
+      	if (This->chanbuf) IRpcChannelBuffer_Release(This->chanbuf);
         HeapFree(GetProcessHeap(),0,This);
     }
     return ref;