Allow `null` for fields in `Comment` constructor
Allow `null` for fields in `Comment` constructor

All core fields (name, email-address, website-address) can now be set to `null` when creating a `Comment`. This uses the new, private `null_empty_escape` function to return `null` for `null` or whitespace values and escape all other values. This fixes not setting the name field to `null` for whitespace only values.

Addpixel/KirbyComments,Addpixel/KirbyCommentsPlugin