Fix null pointer deref in pending check

Depending on how some uninitialized data was prepopulated, the ibsend
check was periodically crashing out in the call to
MPID_Request_is_pending_failure. Some simple sanity checking to make
sure the input data wasn't NULL takes care of this.
Signed-off-by: Huiwei Lu <huiweilu@mcs.anl.gov>

src/mpid/ch3/src/mpid_comm_failure_ack.c

@@ -158,6 +158,10 @@ int MPID_Request_is_pending_failure(MPID_Request *request_ptr)
     MPIDI_STATE_DECL(MPID_STATE_REQUEST_IS_PENDING_FAILURE);
     MPIDI_FUNC_ENTER(MPID_STATE_REQUEST_IS_PENDING_FAILURE);
 
+    if (NULL == request_ptr || NULL == request_ptr->comm) {
+        goto fn_exit;
+    }
+
     if (request_ptr->dev.match.parts.rank != MPI_ANY_SOURCE) {
         goto fn_exit;
     }