compatibility with php 5.3

After upgrading to php 5.3 I started getting lots of errors like this:

Warning: Attempt to modify property of non-object in [site path]/modules/calendar/includes/calendar_plugin_display_page.inc

Warning: Attempt to modify property of non-object in [site path]/modules/calendar/includes/calendar_plugin_display_block.inc

Warning: Attempt to modify property of non-object in [site path]/modules/calendar/includes/calendar_plugin_display_attachment.inc

Based on a workaround for a related issue with Date (http://drupal.org/node/549884#comment-2067884) I have produced a patch file which simply wraps the offending code with this:

if (is_object($display)){
.....
}

This gets rid of the error messages, but doesn't address the real problem, which is why the code is trying to treat an array like an object. Simply deleting the offending lines may well have achieved the same thing but I don't know enough about the module to be sure