Sanity checks for calls that were causing crashes

src/cpp/server/server.cc

@@ -287,12 +287,14 @@ void Server::Wait() {
 }
 
 void Server::PerformOpsOnCall(CallOpBuffer* buf, Call* call) {
+  if (call->call()) {
     static const size_t MAX_OPS = 8;
     size_t nops = MAX_OPS;
     grpc_op ops[MAX_OPS];
     buf->FillOps(ops, &nops);
     GPR_ASSERT(GRPC_CALL_OK ==
                grpc_call_start_batch(call->call(), ops, nops, buf));
+  }
 }
 
 class Server::AsyncRequest GRPC_FINAL : public CompletionQueueTag {
@@ -343,7 +345,9 @@ class Server::AsyncRequest GRPC_FINAL : public CompletionQueueTag {
     }
     ctx_->call_ = call_;
     Call call(call_, server_, cq_);
+    if (call_) {
       ctx_->BeginCompletionOp(&call);
+    }
     // just the pointers inside call are copied here
     stream_->BindCall(&call);
     delete this;