Trying to get a records custom field breaks pages?

[InfinityRazz]

Am trying to make a block to display a base 64 encoded string to an image. Once upon a time i had this working, though have sadly long lost the code;
According to here, to ref my custom field all i'd need to add is {$record->customFieldDisplayByKey('base_string', 'listing')|raw}, yet adding this single line breaks everything immediately. : 

Anyone care to point my in the right direction of what i'm doing wrong exactly? 🙃
This also generates a HUGE error log that i have no idea how to make heads or tails of 🤷‍♂️

 

[Matt]

Can you share the HTML code you're using and the error it generates?