Refs #29155 -- Fixed LookupTests.test_pattern_lookups_with_substr() crash on Oracle.
Refs #29155 -- Fixed LookupTests.test_pattern_lookups_with_substr() crash on Oracle.

Test introduced in feb683c4c2c5ecfb61e4cb490c3e357450c0c0e8 revealed
unexpected behavior on Oracle that allows concatenating NULL with string.
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