Steps to reproduce:
1. Open attached project "case_813052-MeshFilterCrash.zip"
2. Open "_BlurryRefraction" scene.
3. Select "_RefractiveGlass" in hierarchy.
4. Set Mesh Filter to "none".
5. Enter play mode.
6. Unity crashes.

Reproduced with: 5.4.0b22, 5.4.0b24, 5.4.0b25, 5.5.0a3.
Not reproduced with: 5.2.4f1, 5.3.5f1, 5.3.5p8.

Workaround: insert this code
MeshFilter meshFilter = this.GetComponent<MeshFilter>();
if (meshFilter == null || meshFilter.sharedMesh == null)
return;