Deprecated function: strpos(): Passing null to parameter #1 ($haystack) of type string is deprecated

Steps to reproduce (Problem/Motivation)

I have created a custom block with two contextual filters. first one has the multiple values enabled and the other is a singular value. When cache refreshing i get an error that says:

Deprecated function: strpos(): Passing null to parameter #1 ($haystack) of type string is deprecated in Drupal\entity\QueryAccess\ViewsQueryAlter->mapConditions() (line 166 of modules/contrib/entity/src/QueryAccess/ViewsQueryAlter.php).

Proposed resolution

Add a check if the "$field" variable exists in the first place