Using awk, how would you assign 'null' a value to read?

I'm sure there's a set character for this, I just can't find it.

For example,

I've got a string of awk like this:

awk '
$3==24{print "stuff"}
$3==23{print "stuff"}
'

I need to know how to account for blank colums using the same format so that if $3 = blank {print "stuff"}

Thanks!

bash awk
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