Since November 2017 I have received three bug reports from users who see this error when running any command in the choroplethr package:

Theme element panel.border missing
  Error in if (theme$panel.ontop) { : argument is of length zero

Normally when someone reports a choroplethr bug that I cannot reproduce I recommend they do the following:

1. Update to the latest version of R and RStudio.
2. Type “update.packages(ask=FALSE)” to get the latest version of each package.
3. Restart R and try again.

However, each of the three users has tried this it has not solved their problem.

It appears that the bug is at least somewhat OS dependent. I am running the following version of R:

R version 3.4.3 (2017-11-30)
Platform: x86_64-apple-darwin15.6.0 (64-bit)
Running under: macOS High Sierra 10.13.3

and I cannot reproduce the bug. The users who report the bug have these configurations:

version R version 3.4.3 (2017-11-30)
 system x86_64, linux-gnu    

version R version 3.4.3 (2017-11-30)
 system x86_64, linux-gnu

R version 3.4.1 (2017-06-30)
 Platform: x86_64-w64-mingw32/x64 (64-bit)
 Running under: Windows Server 2008 R2 x64 (build 7601) Service Pack 1

Because I do not have access to a machine configuration that produces the bug, I am limited in my ability to debug this.

A google search for this error shows that issues #179 (a linux machine) and #185 (no OS specified) in the ggmap package both report the same error and were filed at roughly the same time that I started receiving these error reports. These issues seem to have been resolved by this change. However, since I am not able to reproduce the error on my own machine, I am reluctant to make any updates to the choroplethr code base based on what I see in that commit.

If you are able to shed some light on what is going on with this bug, then please leave a comment below.

The following code seems to reproduce the bug:

library(choroplethr)
library(choroplethrMaps)
data(df_pop_state)
state_choropleth(df_pop_state)

Update

Thank you for everyone who provided test results in the comments. I have been able to narrow down the issue to occurring in the development version of ggplot2. That is, the OS issue appears to be a red herring. I am now working on the issue.