fix: catch variable shadows closure parameter causing "Undefined variable $exception" on PHP 8.0+

[aasimsajjad22]

Fixes #7

The catch variable $exception shadows the closure parameter of the same name. In PHP 8.0+, catch clause variables are unset after the catch block exits — this destroys the closure parameter too. The throw $exception on the line after the catch block then fails with Error: Undefined variable $exception.

Fix is to rename the catch variable to $caughtError so it doesn't shadow the closure parameter.