BibTex - the literal stack isn't empty for entry

Question

How to get rid of this .bib error, please?

Database file #1: ref.bib ptr=1, stack= 2014 ---the literal stack isn't empty for entry Berio2014 while executing---line 1719 of file caosp306.bst

The entry is:

@inproceedings{Berio2014,
author = {Berio, Philippe and Bresson, Y. and Clausse, J. and Mourard, D. and Dejonghe, J. and Duthu, A. and Lagarde, S. and Meilland, A. and Perraut, Karine and Tallon-Bosc, Isabelle and Nardetto, N. and Spang, Alain and Bailet, C. and Marcotto, A. and Chesneau, O. and Stee, P. and Feautrier, P. and Balard, P. and Gach, Jean-Luc},
year = {2014},
month = {07},
pages = {914616},
title = {Long baseline interferometry in the visible: The FRIEND project},
volume = {9146},
booktitle = {Long baseline interferometry in the visible: The FRIEND project},
journal = {Proceedings of SPIE - The International Society for Optical Engineering},
doi = {10.1117/12.2054890}
}

File.tex:

\documentclass[11.5]{caosp306}
\bibliographystyle{caosp306}
\begin{document}
\nocite{*}
\bibliography{ref.bib}
\end{document}

Answer 1

The bst does not seem to like it when you specify volume but not series. Remove the volume or add a series to solve the issue.

Note also that your reference is not fully correct: the title and booktitle are the same and an @inproceedings entry should not have a journal, and probably also not a series or volume at all.

If you download the reference in BibTeX format from https://www.spiedigitallibrary.org/conference-proceedings-of-spie/9146/914616/Long-baseline-interferometry-in-the-visible-the-FRIEND-project/10.1117/12.2054890.short?SSO=1 then you get a version that looks more correct than the one provided in the question here. However this version still contains a volume field that triggers the error. Removing that field results in a succesful run.

Working version with both entries, first entry corrected from the question, second entry from the publisher website:

@inproceedings{Berio2014,
   author = {Berio, Philippe and Bresson, Y. and Clausse, J. and Mourard, D. and Dejonghe, J. and Duthu, A. and Lagarde, S. and Meilland, A. and Perraut, Karine and Tallon-Bosc, Isabelle and Nardetto, N. and Spang, Alain and Bailet, C. and Marcotto, A. and Chesneau, O. and Stee, P. and Feautrier, P. and Balard, P. and Gach, Jean-Luc},
    title = {Long baseline interferometry in the visible: The FRIEND project},
booktitle = {Proceedings of SPIE - The International Society for Optical Engineering},
     year = {2014},
    month = {07},
    pages = {914616},
      doi = {10.1117/12.2054890},
}

@inproceedings{10.1117/12.2054890,
author = {P. Berio and Y. Bresson and J. M. Clausse and D. Mourard and J. Dejonghe and A. Duthu and S. Lagarde and A. Meilland and K. Perraut and Isabelle Tallon-Bosc and N. Nardetto and A. Spang and C. Bailet and A. Marcotto and O. Chesneau and P. Stee and P. Feautrier and P. Balard and J. L. Gach},
title = {{Long baseline interferometry in the visible: the FRIEND project}},
booktitle = {Optical and Infrared Interferometry IV},
editor = {Jayadev K. Rajagopal and Michelle J. Creech-Eakman and Fabien Malbet},
organization = {International Society for Optics and Photonics},
publisher = {SPIE},
pages = {347 -- 357},
keywords = {Long baseline interferometry, optical fiber, visible interferometry, instrumentation},
year = {2014},
doi = {10.1117/12.2054890},
URL = {https://doi.org/10.1117/12.2054890}
}

Result:

Answer 2

I agree with @Marijn's answer. For me, the error exists when one citation is @inproceedings but doesn't have the booktitle property. Once I added the associated property, booktitle={xxx}, the error disappeared.