Reported by Vivit-R, the chance of freeing a monster from being
trapped in a web was very small and failure resulted in creation of
a new web at the hero's spot, eventually making it impossible to
attempt to #untrap the monster (if hero escaped the new web and moved
to another spot adjacent to trapped monster, eventually surrounding
it with webs). [That's actually misleading. Escaping the new web
but staying at the same spot lets the player try again; repeat as
needed.... But chance of failure still seemed way too high.]
This reduces the chance of failure from 29/30 to 6/7 and makes the
chance of spreading the web after failure be 1/3 instead of 100%. It
also supplies missing feedback about the monster still being trapped
if the attempt to make a new web fails.
Closes#608
d26537c4c9