Fix the Dijkstra function's random behavior

[sirkotal]

The Graph's dijkstra function is showcasing some signs of random behavior (for the same pair of stations, it is returning both 32 and 20).

[sirkotal]

The min cost path is now being stored correctly, the bottleneck function is also working fine, but the function itself isn't prioritizing the shortest path (it sometimes stores paths with double the size/cost).