added try catch in computeifpresent to preserve old value incase of e…

[asureshraja]

added try catch in computeifpresent to preserve old value incase of errors Issue 5438 - https://github.com/google/guava/issues/5438

[ben-manes]

Ideally fix the formatting to Google's style guide, but maybe if merged that person will do it.

You might want to run Caffeine's test suite against your new dependency. You can use jitpack.io or a file dependency, and update the non-atomic computes from GuavaCacheFromContext. It runs many tests to 1-2hrs if the full suite.