Php 5.3 notice context_block_classes

I think I found a PHP 5.3 notice-level bug. When module is enabled I get

Notice: Undefined index: context_block_classes in context_block_class_reaction_block_class->execute() (line 84 of (path)/sites/all/modules/context_block_class/plugins/context_block_class_reaction_block_class.inc).

I think it's possible judging by other PHP5.3 bug reports that the ampersand in the incoming variable is causing this problem.. so line 68 could be
function execute($vars)
instead? Just an idea as I don't know how the module works really.

68 	 function execute(&$vars) {
....
80 	if (!empty($v->reactions[$this->plugin][$region]['blocks'][$bid])) {
81 	$classes[$v->reactions[$this->plugin][$region]['blocks'][$bid]['class']] = $v->reactions[$this->plugin][$region]['blocks'][$bid]['class'];
82 	}
83 	}
84 	$vars['context_block_classes'] .= !empty($classes) ? ' '. implode(' ', $classes) : '';
85 	} 

Thanks -- I could be completely wrong tho.