The Windows 10 spring update, or "April 2018 Update" build 17133 was supposed to be the version that shipped to everyone starting nine days ago on April 10, but "reliability issues" blocked it from being the absolute RTM build, despite a cumulative update (17133.73) being released that could have fixed those issues. In an unprecedented move by Microsoft, a second RTM candidate (build 17134.1) was released a couple of days ago, but it seems this too has a bug that needs squashing.
Several users are reporting on Reddit that the setting: "Set defaults by app" is crashing when people try to launch it, as shown above. You can test if it is affecting your system on builds 17133 and 17134 by heading to Settings > Apps > Default apps > Set defaults by app > Set defaults by app.
I personally was unable to reproduce the bug on a (relatively old) ASUS P5K-E Intel i5-4440 system with 16GB of DDR3 RAM, I am running build 17134.1 that I upgraded over 17133.73. It"s unclear from the comments what sort of systems are affected or if those experiencing it upgraded or clean installed, since those details are scarce from the Reddit thread.
What we can determine from those that responded is that at least one user said that the bug appeared after upgrading to build 17134; the bug also appears on French, Italian and English systems so it isn"t language specific, and as of writing, I am unable to find it in the Feedback Hub, so I hope that someone who actually has the bug (I don"t) will report it.
Microsoft has yet to comment through its various channels to acknowledge the bug, although (hopefully) this might be something that can be fixed with a cumulative update.
Source: Reddit via WindowsLatest
Update: The bug is in the Feedback Hub under Desktop Environment > Settings "settings crashes whenever I try to access any links in build 17634" and although it was submitted from the Skip Ahead build, people on build 17134 have upvoted it too.