If response body does not have ContentType plugin crash

[leoleitemelo]

At FetchPlugin.java line 123, when trying to check if response is a image if the response does not have ContentType it throw null pointer exception.
This changes address this issue for me
at line 123 i change from
if (response.body().contentType().type().equals("image")) {

to

if (response.body().contentType() != null && response.body().contentType().type().equals("image")) {