BGE bug #30555: crash in Replace Mesh when physics shape is triangle mesh and new mesh has no collision faces. The fix consists in keeping the previous physics shape, which is not quite correct, but the situation is unusual anyway.

source/gameengine/Physics/Bullet/CcdPhysicsController.cpp

@@ -1918,6 +1918,10 @@ bool CcdShapeConstructionInfo::UpdateMesh(class KX_GameObject* gameobj, class RA
 			}
 		}
 
+		// This case happens when none of the polys are colliders
+		if (tot_bt_tris == 0 || tot_bt_verts == 0)
+			return false;
+
 		m_vertexArray.resize(tot_bt_verts*3);
 		btScalar *bt= &m_vertexArray[0];