If the module registry contains a null entry (e.g. Blossom produced null module name in definition metadata, see PR for BLOSSOM-272 for remediation), then the corresponding column filter's data-provider might suffer from that, and produce an NPE when opening the app.

UI's CaptionFilteringDataProviderWrapper computes its size from plain Stream#count, and since the wrapped data-provider ModuleDefinitionSelectFieldSupport.ModuleDefinitionDataProvider#fetch returns a stream with distinct/sorted operations, Stream#count attempts (and fails) to compare distinct null entries, hence no count.

java.lang.NullPointerException: null
        at java.util.Comparators$NaturalOrderComparator.compare(Comparators.java:52) ~[?:1.8.0_144]
	...
        at java.util.stream.SortedOps$RefSortingSink.end(SortedOps.java:387) ~[?:1.8.0_144]
	at java.util.stream.DistinctOps$1$2.end(DistinctOps.java:168) ~[?:1.8.0_144]
        ...
	at java.util.stream.ReferencePipeline.count(ReferencePipeline.java:526) ~[?:1.8.0_144]
	at info.magnolia.ui.contentapp.CaptionFilteringDataProviderWrapper.size(CaptionFilteringDataProviderWrapper.java:95) ~[magnolia-ui-framework-6.2.1.jar:?]