CLI: Fix handling of command options in help display

[medikoo]

Listing help for commands with no options object configured, resulted with following error:

 Type Error ---------------------------------------------
 
  TypeError: Cannot convert undefined or null to object
      at Function.entries (<anonymous>)
      at CLI.displayCommandOptions (/Users/medikoo/npm-packages/serverless/lib/classes/CLI.js:154:12)
      at CLI.generateCommandsHelp (/Users/medikoo/npm-packages/serverless/lib/classes/CLI.js:353:10)
      at CLI.displayHelp (/Users/medikoo/npm-packages/serverless/lib/classes/CLI.js:116:16)
      at Serverless.run (/Users/medikoo/npm-packages/serverless/lib/Serverless.js:147:18)
      at /Users/medikoo/npm-packages/serverless/scripts/serverless.js:50:26
 

It's a regression introduced with #8280

This patch fixes that

[codecov-io]

Codecov Report

Merging #8476 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #8476   +/-   ##
=======================================
  Coverage   87.37%   87.37%           
=======================================
  Files         255      255           
  Lines        9472     9472           
=======================================
  Hits         8276     8276           
  Misses       1196     1196           

Impacted Files	Coverage Δ
lib/classes/CLI.js	93.36% <ø> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update c0a2ecf...6b46ae0. Read the comment docs.