Hi,
I added a comment about the errors to Bugzilla.
Besides this specific errors, this remembered me to a general issue with the graphics. The structure is inherited from the way graphing was/is done in Smoothwall/IPCop: The graphics are generated periodically and saved to files. The WUI just displays these graphic files. Errors in generation are printed to stdout. IPFire generates the graphics on-the-fly ( graphics data are output to stdout and thus embedded directly into the HTML code ). An error output to stdout gives an invalid graphic element. Therefore we should redesign the interface to these graphing functions allowing a return of errors. I once have found a solution ( I think in assisting in development of OVPN graphs ), but don't remember it in the moment.
UPDATE to my former post: I've found the changed files. The 'print' ( to stdout ) is simply changed to a call of General::log. The lines read now:
&General::log("Error in RRD::graph for .....: ".$ERROR)if $ERROR
Bernhard