Reset the entire transformation when merging

This fixes the issue when the packing algorithm rotated an object

CURA-7796

cura/CuraApplication.py

@@ -1522,13 +1522,10 @@ class CuraApplication(QtApplication):
 
         # Move each node to the same position.
         for mesh, node in zip(meshes, group_node.getChildren()):
-            transformation = node.getLocalTransformation()
-            transformation.setTranslation(zero_translation)
-            transformed_mesh = mesh.getTransformed(transformation)
-
+            node.setTransformation(Matrix())
             # Align the object around its zero position
             # and also apply the offset to center it inside the group.
-            node.setPosition(-transformed_mesh.getZeroPosition() - offset)
+            node.setPosition(-mesh.getZeroPosition() - offset)
 
         # Use the previously found center of the group bounding box as the new location of the group
         group_node.setPosition(group_node.getBoundingBox().center)