biblatex-chicago patch for months with no issue or number (with MWE)

chicago-authordate.bbx.diff

2694c2694
<   \ifthenelse{\iffieldundef{issue}%\AND\iffieldundef{month}
---
>   \ifthenelse{\iffieldundef{issue}\AND\iffieldundef{month}
2877a2878
> 

chicago.bbl

% $ biblatex auxiliary file $
% $ biblatex bbl format version 2.3 $
% Do not modify the above lines!
%
% This is an auxiliary file used by the 'biblatex' package.
% This file may safely be deleted. It will be recreated by
% biber as required.
%
\begingroup
\makeatletter
\@ifundefined{[email protected]}
  {\@latex@error
     {Missing 'biblatex' package}
     {The bibliography requires the 'biblatex' package.}
      \aftergroup\endinput}
  {}
\endgroup


\refsection{0}
  \sortlist{entry}{nty}
    \entry{ritchie1993}{article}{}
      \name{labelname}{1}{}{%
        {{hash=42af644cbe8be3fb0872492484150c5e}{Ritchie}{R\bibinitperiod}{Dennis\bibnamedelima M.}{D\bibinitperiod\bibinitdelim M\bibinitperiod}{}{}{}{}}%
      }
      \name{author}{1}{}{%
        {{hash=42af644cbe8be3fb0872492484150c5e}{Ritchie}{R\bibinitperiod}{Dennis\bibnamedelima M.}{D\bibinitperiod\bibinitdelim M\bibinitperiod}{}{}{}{}}%
      }
      \list{location}{1}{%
        {New York, NY, USA}%
      }
      \list{publisher}{1}{%
        {ACM}%
      }
      \strng{namehash}{42af644cbe8be3fb0872492484150c5e}
      \strng{fullhash}{42af644cbe8be3fb0872492484150c5e}
      \field{sortinit}{R}
      \field{labelyear}{1993}
      \field{labelmonth}{03}
      \field{datelabelsource}{}
      \field{labeltitle}{The Development of the C Language}
      \field{issn}{0362-1340}
      \field{journaltitle}{SIGPLAN Not.}
      \field{month}{03}
      \field{number}{3}
      \field{title}{The Development of the C Language}
      \field{volume}{28}
      \field{year}{1993}
      \field{pages}{201\bibrangedash 208}
      \verb{doi}
      \verb 10.1145/155360.155580
      \endverb
      \verb{url}
      \verb http://doi.acm.org/10.1145/155360.155580
      \endverb
    \endentry
  \endsortlist
\endrefsection
\endinput

chicago.bib

@Article{ritchie1993,
  Title                    = {The Development of the C Language},
  Author                   = {Ritchie, Dennis M.},
  Journal                  = {SIGPLAN Not.},
  Year                     = {1993},

  Month                    = {March},
  Number                   = {3},
  Pages                    = {201--208},
  Volume                   = {28},

  Acmid                    = {155580},
  Address                  = {New York, NY, USA},
  Doi                      = {10.1145/155360.155580},
  ISSN                     = {0362-1340},
  Issue_date               = {March 1993},
  Numpages                 = {8},
  Owner                    = {wchargin},
  Publisher                = {ACM},
  Url                      = {http://doi.acm.org/10.1145/155360.155580}
}

chicago.log

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**chicago.tex
(./chicago.tex
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(./chicago.aux)
\openout1 = `chicago.aux'.

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Package biblatex Info: No input encoding detected.
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Package biblatex Info: Automatic encoding selection.
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\openout3 = `chicago.bcf'.

Package biblatex Info: Trying to load bibliographic data...
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Package logreq Info: Writing requests to 'chicago.run.xml'.
\openout1 = `chicago.run.xml'.

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PDF statistics:
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chicago.tex

\documentclass{article}

\usepackage[style=chicago-authordate,backend=biber]{biblatex}
\addbibresource{chicago.bib}
\nocite{*}

\begin{document}

\printbibliography

\end{document}

.log and .bbl files created with

$ rm chicago.!(tex|bib)
$ pdflatex chicago.tex
$ biber chicago
$ pdflatex chicago.tex
$ pdflatex --version
pdfTeX 3.1415926-2.5-1.40.14 (TeX Live 2013/Debian)
kpathsea version 6.1.1
Copyright 2013 Peter Breitenlohner (eTeX)/Han The Thanh (pdfTeX).
There is NO warranty.  Redistribution of this software is
covered by the terms of both the pdfTeX copyright and
the Lesser GNU General Public License.
For more information about these matters, see the file
named COPYING and the pdfTeX source.
Primary author of pdfTeX: Peter Breitenlohner (eTeX)/Han The Thanh (pdfTeX).
Compiled with libpng 1.2.49; using libpng 1.2.50
Compiled with zlib 1.2.8; using zlib 1.2.8
Compiled with poppler version 0.24.5

This is from a vanilla TeXlive install via sudo apt install texlive on Linux Mint 17.3 (version 2013.20140215-1).