@petebacondarwin @btford @IgorMinar

Code sample: http://plnkr.co/edit/Ly2gfBsyd1J4iJlTjA4C
To reproduce:

• http://run.plnkr.co/plunks/Ly2gfBsyd1J4iJlTjA4C/#/x1 (loads the child component correctly)
• in the same tab, change URL to http://run.plnkr.co/plunks/Ly2gfBsyd1J4iJlTjA4C/#/x2 (stack trace)

Note that navigating directly to the incorrect URL does not seem to trigger the issue; only navigating from a valid to an invalid route in the context of the same tab does.

Attempted fix: #7203