This is a common crash that has occurred since at least 4.16.
The callstack is nearly identical to [Link Removed], which appears to be fixed in 4.18; and [Link Removed], which has not. The difference is that this callstack specifically references UMaterialFunctionThumbnailRenderer::Draw.
I believe this was fixed.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-51781 in the post.