Some time ago I discussed the problem that calling a reference to a nonexistent node when generating .info files.
When outputting html, reference to nonexistent node also gives a problem. @ref reference to nonexistent node `igc03--Sicl--CircAmRg' Problem is aggravated because the failure stops the generation of any files. When using texi2pdf, one gets in the output pdf document <undefined> [igc03–Sicl–CircAmRg], page <undefined>, This is much better than not generating any output. I have read some innovative ideas from Language Designer Luca Saiu, to make programs run even with errors. These ideas will certainly be interesting, because as with the pdf output, the difficulties are transplanted in the output. Then one can eventually go and fix them. However, the problem with undefined ref will not stop the author from continuing with his work until he resolves undefined ref. I mention this also for the generation of .info files.
