Your question raises a couple of issues. The most obvious is that A5 is half the size of A4, so it is difficult to see how you will get four A5 cards to the A4 page.
Normally when a field is blank, and that field is in a line by itself e.g as in an address block, the missing field simply leaves an empty line i.e. the 'missing line' that you describe. Replacing the field with a paragraph break (what you describe as a carriage return) would give you an extra 'missing line'. How are your fields laid out on the 'cards'?
With four records to a page, you should be thinking in terms of a label merge document.

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Graham Mayor - MS MVP (Word) (2002-2019)
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