It seems like $section can also be of type null; however, parameter $section of BitBag\SyliusCmsPlugin\E...Interface::addSection() does only seem to accept BitBag\SyliusCmsPlugin\Entity\SectionInterface, maybe add an additional type check?
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Ignorable by Annotation
)
If this is a false-positive, you can also ignore this issue in your code via the ignore-type annotation