update-report: silence exception.

We don't care if the formula isn't available here. I've seen this a few
times with added formulae when my homebrew-core is on a non-master
branch.

Library/Homebrew/cmd/update-report.rb

@@ -226,6 +226,9 @@ class Reporter
           new_version = formula.pkg_version
           old_version = FormulaVersions.new(formula).formula_at_revision(@initial_revision, &:pkg_version)
           next if new_version == old_version
+        rescue FormulaUnavailableError
+          # Don't care if the formula isn't available right now.
+          nil
         rescue Exception => e # rubocop:disable Lint/RescueException
           onoe "#{e.message}\n#{e.backtrace.join "\n"}" if ARGV.homebrew_developer?
         end