Fix T75383:Bevel weird behaviour when using bevel weights

Don't use the cube corner special case when the offsets are different
for the three edges involved. The generic VMesh for this situation isn't
perfect, but it's much better than a failed cube corner VMesh.

Tests pass.

source/blender/bmesh/tools/bmesh_bevel.c

@@ -4167,6 +4167,10 @@ static int tri_corner_test(BevelParams *bp, BevVert *bv)
   if (bv->vmesh->count != 3) {
     return 0;
   }
+
+  /* Only use the tri-corner special case if the offset is the same for every edge. */
+  float offset = bv->edges[0].offset_l;
+
   totang = 0.0f;
   for (i = 0; i < bv->edgecount; i++) {
     e = &bv->edges[i];
@@ -4178,6 +4182,11 @@ static int tri_corner_test(BevelParams *bp, BevVert *bv)
     else if (absang >= 3.0f * (float)M_PI_4) {
       return -1;
     }
+
+    if (e->is_bev && !compare_ff(e->offset_l, offset, BEVEL_EPSILON)) {
+      return -1;
+    }
+
     totang += ang;
   }
   if (in_plane_e != bv->edgecount - 3) {