Fix initialization.
Merge topic 'fix-genex-preprocessing-incomplete' into next

e321f00 Fix initialization.
genex: Fix preprocessing with incomplete content (#14410).

Similar incomplete generator expressions are already tested
in the GeneratorExpression unit test, but those are executed
with add_custom_target. The generator expressions in the include
directories are run through the preprocessor, whereas the ones
run through add_custom_target are not.
Merge topic 'fix-genex-preprocessing-incomplete' into next

70089d0 genex: Fix preprocessing with incomplete content (#14410).
Genex: Test preprocessing incomplete expressions.
Merge topic 'fix-genex-preprocessing-incomplete-test' into next

8564bcb Genex: Test preprocessing incomplete expressions.