When using the query operator Does Not Contain on fields with text values, blank results are omitted in The Raiser's Edge 7.93, whereas they were included in results using same query criteria in The Raiser's Edge 7.92.
Download and install the latest patch, which contains all fixes from previous patches. If you are running an older version, download and install the latest version and then the patch.
In The Raiser's Edge 7.93, use a query criteria as follows if Does Not Contain needs to consider blank values:
(<field> does not contain <enter your text> OR <field> blank)