Unnecessary NULL checks and multiple Null checks

[shivramsrivastava]

NULL check is done in so many places where it is not required.

eg:- CHECK_NOTNULL(res_node);//there is no operation is done on it just passing to another function.

void FlowGraphManager::UpdateResourceNode(
FlowGraphNode* res_node,
queue<TDOrNodeWrapper*>* node_queue,
unordered_set<uint64_t>* marked_nodes) {
CHECK_NOTNULL(res_node);
UpdateResOutgoingArcs(res_node, node_queue, marked_nodes);
}

void FlowGraphManager::UpdateFlowGraph(
queue<TDOrNodeWrapper*>* node_queue,
unordered_set<uint64_t>* marked_nodes) {
CHECK_NOTNULL(node_queue);
CHECK_NOTNULL(marked_nodes); //Not required
while (!node_queue->empty()) {
TDOrNodeWrapper* cur_node = node_queue->front();
node_queue->pop();
if (!cur_node->node_) {
// We're handling a task that doesn't have an associated flow graph node.
UpdateChildrenTasks(cur_node->td_ptr_, node_queue, marked_nodes);
delete cur_node;
continue;
}
if (cur_node->node_->IsTaskNode()) {
UpdateTaskNode(cur_node->node_, node_queue, marked_nodes);
UpdateChildrenTasks(cur_node->td_ptr_, node_queue, marked_nodes);
} else if (cur_node->node_->IsEquivalenceClassNode()) {
UpdateEquivClassNode(cur_node->node_, node_queue, marked_nodes);
} else if (cur_node->node_->IsResourceNode()) {
UpdateResourceNode(cur_node->node_, node_queue, marked_nodes);
} else {
LOG(FATAL) << "Unexpected node type: " << cur_node->node_->type_;
}
delete cur_node;
}

Note: have reservation that there are multiple NULL check as well present in the code