[Pharo-project] facetious Splitter

Recipe for a nice scrambling of layouts in Pharo 10102: open a FileList; single click the splitter above text; you should see an annoying mess in the pane layouts. This happens with some other tools (like FileContentsBrowser). Removing the list of files morph with the halos, I discovered a hidden splitter under top buttons. You can see the mess in Pharo when acting on these two splitters. Note that 3.9 ad 3.10.2 images have the hidden splitter too, but the splitters behaves better. So it has to be a Pharo change. Unfortunately morphs are hard to debug! It would probably be easier to trace recent Morphic changes. Any clue? Nicolas