Revert "Fix path comparison"

This reverts commit cc2c32d.

Co-authored-by: claudiolor <[email protected]>

src/GraphParallelDFS.cpp

@@ -184,7 +184,7 @@ void GraphParallelDFS::convertToDT() {
                         // update the path in the case in which
                         // - The path is empty, so this is the first time we meet this child
                         // - We found a path Br which is better than the current one
-                        if(this->parents[child] == -1 || Br <= Qr){
+                        if(Qr.empty() || Br <= Qr){
                             paths[child] = Br;
 
                             // the previous one, if existing, is a parent in the dag which is not present in the dt