Entity field content type rendering with limit/offset accidentally modifies entity

Steps to reproduce (using Panels):
- create a content type with a field that allows multiple values
- create a node from that content type that contains two values A and B
- create a panel with the new node as its context
- add the field to the panel with "offset = 0" and "limit = 1"
- add the same field to the panel again with "offset = 1" and "limit = 1"
- add the same field to the panel a third time with "offset = 0" and "limit = 1"

Expected:
Three field panes with values A, B, A

Result:
The first field pane is rendered correctly with value A, but then the entity's field value is permanently limited to only contain the 1st item in the field. The second pane tries to get the 2nd of an array that now contains only one element and the result is naturally empty. The third pane tries to get the 1st item of an array that now contains no elements at all and is also rendered empty.

The Problem:
In file plugins/content_types/entity_context/entity_field.inc

function ctools_entity_field_content_type_render($subtype, $conf, $panel_args, $context) {
...
  $clone = clone $entity;
  $clone->{$field_name}[$language] = $all_values;
  $field_output = field_view_field($entity_type, $clone, $field_name, $field_settings, $language);
...
}

Clone doesn't do what the original developer probably thought it would. It creates a shallow clone of the entity. Consequently, setting the value of $clone->{$field_name}[$language] also changes the value for the original entity. All subsequent access to that field value in the same request returns the modified array. So, in the example from above (and pseudo-code):

orig = [A, B]
// first access
v = orig.filter(0, 1) // orig = v = [A]
// second access
v = orig.filter(1, 1) // orig = v = []
//third access
v = orig.filter(0, 1) // orig = v = []

I have directly attached a patch that (in my tests) fixes the issue without causing any side effects (the patch should also be applicable to the current HEAD). There is probably a more reasonable way of fixing this using Drupal APIs, but I'm still quite new to Drupal and didn't find anything useful.