[tests] Return an empty array if nowJson.builds is empty (#3886)
[tests] Return an empty array if nowJson.builds is empty (#3886)

* return an empty array if nowJson.builds is empty
  * https://github.com/zeit/now/pull/3622#issuecomment-578995344
  * extracted from PR discussion
    * occur after following change https://github.com/zeit/now/pull/3622/commits/a645d4ee882b798c01706f106efd3c5c103ca048
  * kudos to @styfle

/cc @styfle
zeit/now-cli,zeit/now-cli,zeit/now-cli,zeit/now-cli,zeit/now-cli,zeit/now-cli,zeit/now-cli