exposures without spectrograph data should have default messages in all webpages

[sybenzvi]

ZERO and DARK exposures without spectrograph data should have default messages on spectrograph QA pages. This is available on some pages but not all. Pages where default messages are available:

• Camera QA pages (qa-camera-*.html), for example, see this page from 20230211
• Camfiber QA pages (qa-camfiber-*.html), for example, see this page from 20230211
• Guiding QA pages (qa-guide-*.html) see this page from 20230211.

Pages that load but have a missing default message:

• Spectro QA pages (qa-spectro-*.html), for example, see this page from 20230211.

Pages with broken links, giving users the error message ERROR: no data found for input URL:

• Camfiber focalplane QA plots qa-camfiber-*-focalplane_plots.html)
• Camfiber positioning QA plots qa-camfiber-*-posacc_plots.html

[jose-bermejo]

This branch solves for the moment the missing placeholder html file for the spectro QA pages. Will check if the other two can be easily fixed