Fix minor comment typo in encoder.py

[ianand]

Replaced "haved" with "have" for grammatical correctness to improve readability of the comment.

[RahulVadisetty91]

It should only catch specific exceptions e.g. ValueError, not all exceptions, this can hide bugs or unexpected errors.

Correction:
try:
j = word.index(first, i)
new_word.extend(word[i:j])
i = j
except ValueError:
new_word.extend(word[i:])
break