Workaround for cc-test-reporter with SimpleCov 0.18
Workaround for cc-test-reporter with SimpleCov 0.18

This PR fixes the following build error when using
cc-test-reporter with SimpleCov 0.18.

```console
$ #!/bin/bash -eo pipefail
./tmp/cc-test-reporter before-build
COVERAGE=true bundle exec rake spec
./tmp/cc-test-reporter format-coverage --output
tmp/codeclimate.$CIRCLE_JOB.json
Starting test-queue master (/tmp/test_queue_228_47138309905180.sock)

==> Summary (2 workers in 36.1115s)

    [ 1]                         8753 examples, 0 failures, 9 pending
    254 suites in 36.1034s      (pid 160 exit 0 )
    [ 2]                         6772 examples, 0 failures, 2 pending
    239 suites in 36.1054s      (pid 161 exit 0 )

Coverage report generated for RSpec, rspec-1, rspec-2, rspec-fork-163,
rspec-fork-164, rspec-fork-165 to /home/circleci/project/coverage. 21266
/ 21459 LOC (99.1%) covered.
Error: json: cannot unmarshal object into Go struct field input.coverage
of type []formatters.NullInt
Usage:
  cc-test-reporter format-coverage [coverage file] [flags]

Flags:
      --add-prefix string   add this prefix to file paths
  -t, --input-type string   type of input source to use [clover,
cobertura, coverage.py, excoveralls, gcov, gocov, jacoco, lcov,
simplecov, xccov]
  -o, --output string       output path (default "coverage/codeclimate.json")
  -p, --prefix string       the root directory where the
    coverage analysis was performed (default "/home/circleci/project")

Global Flags:
  -d, --debug   run in debug mode

Exited with code exit status 255
```

https://circleci.com/gh/rubocop-hq/rubocop/83619

This patch is a workaround until the following issue will be resolved.
https://github.com/codeclimate/test-reporter/issues/418

tejasbubane/rubocop,maxjacobson/rubocop,tdeo/rubocop,bbatsov/rubocop,tejasbubane/rubocop,rrosenblum/rubocop,maxjacobson/rubocop,maxjacobson/rubocop,deivid-rodriguez/rubocop,jmks/rubocop,tdeo/rubocop,tejasbubane/rubocop,deivid-rodriguez/rubocop,jmks/rubocop,bbatsov/rubocop,rrosenblum/rubocop,deivid-rodriguez/rubocop,jmks/rubocop,tdeo/rubocop,rrosenblum/rubocop