This commit prevents writing to the mesh when sculpting on a non-basis
shape key. Prior to this, we incorrectly were applying changes to the
base mesh, even though those changes were not visible with the shape
keys still active, causing new shape keys to have a copy of the deformed
mesh data.

@@ -7316,3 +7316,3 @@
   }
 
-  apply_translations(translations, verts, positions_orig);
+  Mesh &mesh = *static_cast<Mesh *>(object.data);

@@ -7319,0 +7319,4 @@
+  KeyBlock *active_key = BKE_keyblock_from_object(&object);
+  const bool relative_shapekey_active = active_key != nullptr && active_key != mesh.key->refkey;
+  if (!relative_shapekey_active) {
+    /* If a relative shapekey is active, we do not want to write any data to the original mesh. */

@@ -7319,1 +7323,4 @@
+    apply_translations(translations, verts, positions_orig);
+  }
+
   apply_translations_to_shape_keys(object, verts, translations, positions_orig);