T14553 escaper nulls

[niden]

Hello!

• Type: bug fix
• Link to issue: [BUG/REGRESSION]: Phalcon\Escaper::escapeHtml() no longer accepts null in v4 #14553

In raising this pull request, I confirm the following:

• I have read and understood the Contributing Guidelines
• I have checked that another pull request for this purpose does not exist
• I wrote some tests for this PR
• I have updated the relevant CHANGELOG
• I have created a PR for the documentation about this change

Fixed Phalcon\Escaper::escapeHtml and Phalcon\Escaper::escapeHtmlAttr to allow null values

Thanks

[ruudboon]

Looks good. thnx

[codecov]

Codecov Report

Merging #14554 into 4.0.x will decrease coverage by <.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##            4.0.x   #14554      +/-   ##
==========================================
- Coverage   67.73%   67.73%   -0.01%     
==========================================
  Files         488      488              
  Lines      112556   112562       +6     
==========================================
+ Hits        76245    76247       +2     
- Misses      36311    36315       +4