Improve error handling when logging is enabled

[kaderate]

When logging is enabled and an API call fail with another exception that Net::ReadTimeout, the following exception is raised:

NoMethodError: undefined method '*' for nil (NoMethodError) line += "\n [#{(time * 1000).round(1)}ms] 408 Request Timeout #{params}\n" ^

The cause is the time parameter here is not initialized properly and can nil in the case described above:

mangopay2-ruby-sdk/lib/mangopay.rb

Line 287 in 46109ce

res, time = nil, nil

[fredericdelordm]

Hello @kaderate, thanks for the feedback. We are looking into it.