Where should I to look for error when I receive the error message "null" in html views or functions?

Where should I to look for error when I receive the error message "null" in html views or functions?

ZC Team,

I'll not insist complaining of the cryptic error messages, it is a well known issue of Creator and there is nothing new to be added, I need only a hint to understand an often meet error message.

Where should I to look for error when I receive the error message null in html views or functions?

Regards,
George