Heroes can appear in the top towers list and try to load invalid images

[DestructivForce]

Heroes can appear in a player's top 3 towers, which attempts to get the image at towers/\<hero name>.

Ex.:

Expected behavior: ignore heroes for top towers, or code a different link for hero images.

[DestructivForce]

After reviewing the code, this seems to occur due to the same reason as #40, rather than a specific issue with heroes being counted as a favorite tower.