I am using the documentclass book and seems to be getting this error message on every page, but nothing visibly broken. Below is my preamble:
\usepackage[a4paper,left=1.5in,right=1.5in,top=1in,bottom=1in]{geometry}
\usepackage{setspace} %for doublespacing
\usepackage{blindtext}
\usepackage{fancyhdr}
\setlength{\parindent}{4em} %spacing of beginning of a new paragraph
\setlength{\parskip}{1em} %spacing between paragraphs
\doublespacing %double spacing
\renewcommand{\cleardoublepage}{\clearpage} %for the headings
Any thoughts?

\documentclassand ending with\end{document}. The code above in itself does not lead to any problems. – gernot Oct 06 '16 at 12:56\clearpage(it is unlikely to be the best way to do whatever is intended) – David Carlisle Oct 06 '16 at 13:12