#151 Mistyped [data] links can destroy notebook visibilty

[Tim Parkinson]

If user makes a typo when embedding a data file - something like:

[data]776/data]

rather than

[data]776[/data]

Then upon save/publish, viewing the entry gives HTTP 500 Internal Server error which Chrome renders as a blank screen (but IE shows the error).
Author's entry list now appears blank too as do any other RHS searches that include the affected entry.

This is recoverable by an administrator changing the database but
a small error like this should not have such a large effect.

Needs a patch for the 2.4 branch as well as a trunk fix.