Fix strict warning of entity_views_plugin_row_entity_view::pre_render(&$values)

Problem/Motivation

The code shouldn't throw any error/warnings/notices.
Currently the module throws following strict warning (tested with latest views-dev):
Strict warning: Declaration of entity_views_plugin_row_entity_view::pre_render() should be compatible with that of views_plugin_row::pre_render() in require_once() (Zeile 11 von modules/entity/views/plugins/entity_views_plugin_row_entity_view.inc).

Is the reference in entity_views_plugin_row_entity_view::pre_render(&$values) necessary?

Proposed resolution

If the reference isn't necessary we should remove it.
If a reference generally makes sense we could change the method signature in views itself?

Remaining tasks

Clarify if the reference is necessary.

User interface changes

none.

API changes

Possibly...