I believe this is an issue with mirror modifier + curve. To reproduce it:
$./blender -b --python-expr "import bpy; bpy.ops.object.add(type='CURVE');bpy.data.objects['Curve'].modifiers.new('mod', 'MIRROR');bpy.context.view_layer.depsgraph.update()
Smooth Vertices Crash
Operating system: Windows-10-10.0.18362 64 Bits
Graphics card: GeForce GTX 1060 6GB/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 417.35
Broken: version: 2.80 (sub 74), branch: master, commit date: 2019-07-11 13:50, hash: rB06312c6d2db8
Short description of error
Blender crashes to desktop after using the Smoothing slider on the Smooth Vertices command.
Exact steps for others to reproduce the error
Select some vertices, launch the Smooth Vertices command, change the smoothing value with the slider. The crash happens at random but it's tested (on my machine) to happen with Smooth Vertices active, though, it may crash in the same random way while using the Undo command too. As can be seen on this video it needs some time to trigger the crash:
I've also noticed a considerable slow down when the view is switched to the "quad" view, and then reverted back to single view (Toggle Maximize Area), as shown on the first part of the video.