I just updated both R (4.1.2) and RStudio (2021.09.0 Build 351). Don't know if this error is associated with one, the other, or both. See the final line for the error message. I get this message when I double click on an existing .Rproj file. I do not get this message when I launch RStudio from the Start menu. I do not get this message when I launch R from the Start menu (that's why I'm starting here).
R version 4.1.2 (2021-11-01) -- "Bird Hippie"
Copyright (C) 2021 The R Foundation for Statistical Computing
Platform: x86_64-w64-mingw32/x64 (64-bit)
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'citation()' on how to cite R or R packages in publications.
Type 'demo()' for some demos, 'help()' for on-line help, or
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Error in if (file.exists(pythonPath)) return(pythonPath) :
argument is of length zero