Further sensor failure

[tbohne]

• too close -> analogous to inf, just the other direction
• sensor doesn't recognize anything due to too close object
• implement + test in sim + describe in thesis

[tbohne]

tested it in the simulation:

• objects that are too close (< min_range) also return inf
• describe it properly in the thesis, not just "look to sky", could also be facing a very clear open area
• simply getting inf when the next object is too close (< min_range) or too far away (> max_range)