Band-Aid for IE10 readattribute test

This is only a Band-Aid fix for 

https://prototype.lighthouseapp.com/projects/8886-prototype/tickets/1631-expected-identifier-error-on-page-load-in-ie-10

as I don't know what other browsers trigger the `PROBLEMATIC_ATTRIBUTE_READING` test I can't fully fix the problem - only work around it for now