nullif('','') on insert

I need to test whether or not a value is null on
insert. 

Example: insert into table (column) values
nullif('',''));
ERROR: column "column" is of type boolean but
expression is of type text.

It works in MSSQL (probably against not standards) but
nonetheless I need to make it work.

I assume it's returning 'NULL' w/ quotes? I don't know
where to look to alter it. I looked into functions but
all I see is how to write "AS queries" or point to
various snippets. I'd rather just alter the nullif
function. 

Is there a function for this or could someone give me
an example to insert NULL? 

Cheers
Matt

    
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