Add protection when a match for 'Tip' fails.
This is a hack fix -- I don't see why the problem is occuring in the first place but it
does thinks like prevent the knowls solutions from operating.
If this _is_ the correct fix it needs to be propagated to other themes.
Merge pull request #229 from mgage/release/2.8_math4jsfix

This looks good.  

I wrongly assumed that there would always be something to use a tool tip on.  This is the appropriate fix to check for that.