Wheelchart error about WCvarB being an undefined control sequence

Question

I’d like to know why I get and how to correct the following error

(./Feb-15-wheel-cal-fro-teach (minex1).aux) ./Feb-15-wheel-cal-fro-teach (minex1).tex:37: Undefined control sequence. \pgfkeyscurrentkey ->\WCvarB

l.37 }

received when compiling the code below. [When I go to scroll mode, the code compiles and generates an image that looks like I want.]

when running this code (based on modifying the code here by @matexmatics.

\documentclass[border=6pt]{standalone}
\usepackage{wheelchart}
\begin{document}
\begin{tikzpicture}
\sffamily
%%%%%%%%%%%%%%%%%%%%%%%%%%%
\pgfkeys{
  /wheelchart,
  arc data dir=1,
  arc data expand=f,
  arc data pos=0.5,
  arc data sep=0,
  data=,
  domain=450:90,
  plot={{#1}:{#2+0.00416*(450-#1)}},
  value=1,
  wheel data pos=0.5,
  wheel data style={
    align=center,
    rotate=\WCmidangle+(\WCmidangle<90?0:(\WCmidangle<270?180:0))
  }
}

\wheelchart[
  arc data=\WCvarA,
  radius={6}{7.5},
  slices style{25,26}={purple,draw=lightgray},
  slices style{27,28}={pink,draw=lightgray},
  slices style{29,30}={magenta,draw=lightgray},
  slices style{57}={darkgray}
]{%
,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,%
}

\end{tikzpicture}
\end{document}

I interpret the error to mean that the package wheelchart expects a WCvarB. Although WCvarB was used in one of the wheelcharts in the code I’m using, it was not in the piece I am modifying. The wheelchart manual refers to WC vars A, B, and C automatically initialized/instantiated (?) and assigned meanings, but I don’t see how WCvarB is expected in this wheelchart.

I tried putting some text in between the commas defining my slices (to see how it reacted to my including something that would be read as the expected WCvarB) but then I couldn’t compile under scroll mode (over 100 errors, it said).

I checked for transcription errors–and added and removed commas where I thought there might be a problem–but couldn’t find any, however I have modified the sample code enough that I wouldn’t know where a comma might be missing or something.

I wasn’t sure exactly what was needed with the pgfkeys call, and when I tried playing with it, either I couldn’t detect a change or I didn’t have compilable code. I’m sure there is unneeded stuff in it since I stripped out the text and labels on this wheelchart call and could remove the other calls in making the minimal.