Display macro does not stop infinite loop

The display macro contains code that should prevent a recursive infinite loop, but that check is not currently working and instead the user experiences a StackOverflow error.

Steps to reproduce:
1. Create a page with the path "Main.Display1.WebHome" with the following content:

display 1

{{display reference="Main.Display2.WebHome" /}}

2. Create a page with the path "Main.Display2.WebHome" with the following content:

display 2

{{display reference="Main.Display1.WebHome" /}}

Expected:
A red box on the page with the macro exception "MacroExecutionException: Found recursive inclusion of document"

Actual:
A red box on the page with the generic exception "StackOverflowException: stack too deep"