Resolving incompatible ruby gems: fast_excel and jira-ruby

Question

I've been using the fast_excel gem to write data to an excel sheet and have recently imported the jira-ruby gem to pull data from Atlassian Jira. As soon as I imported the jira-ruby gem I started getting the below error when trying to use the fast_excel gem:

NoMethodError (undefined method `utc_offset' for nil:NilClass)

Which is being thrown from this chunk of code in the fast_excel gem:

      # Try use Rails' app timezone
      if Time.respond_to?(:zone)
        offset = Time.zone.utc_offset
      else
        offset = 0 # rollback to UTC
      end

A simple test:

require 'jira-ruby'

if Time.respond_to?(:zone)
  offset = Time.zone.utc_offset
else
  offset = 0
end

puts offset

produces NoMethodError (undefined method utc_offset for nil:NilClass), whereas

if Time.respond_to?(:zone)
  offset = Time.zone.utc_offset
else
  offset = 0
end

puts offset

Produces 0 as expected.

Now I can raise an issue with the maintainers of these gems, but in the meantime how can I identify the source of the issue and fix it? Obviously I can monkey around the fast_excel gem source code which would solve the problem locally but our build process pulls these gems down automatically and it would fail there. Any pointers appreciated.