removed a very stupid redundancy
fixed update bug and enhanced load function.

the update bug was due to a bad conditional expression when trying update the
ID dictionaries with a new show or movie id. Because some show ids were mapped
to a single element dictionary as an empty string [''], failed shows didn't
completely satisfy the condition and were treated as movies.

load function now filters out any empty strings when loading ids from the cache
file. conditional checks are much more resilient too.