added comment and formatted code

Author: SamuelHo10

vpr/src/draw/draw_basic.cpp

@@ -592,7 +592,8 @@ void draw_routed_net(ParentNetId net_id, ezgl::renderer* g) {
             draw_state->draw_rr_node[inode].color = DEFAULT_RR_NODE_COLOR;
         }
 
-        if(rr_nodes_to_draw.empty() && rt_node.parent().has_value()) {
+        // When drawing a new branch, add the parent node to the vector to ensure that the conenction is drawn.
+        if (rr_nodes_to_draw.empty() && rt_node.parent().has_value()) {
             rr_nodes_to_draw.push_back(rt_node.parent().value().inode);
         }