The error in grid.callc textbounds, as.graphicsannot(x$label), x$x, x$y, : polygon edge not found error message occurs when there is a misplaced font called when using a ggplot object. It is fixed either by putting the font in the needed location or redirecting the call to the correct location.
Description of the R error
This problem occurs when you are trying to plot data using the ggplot function and using a font theme for its labels. In such cases, the addition of a new font family can cause a problem when going to the graphic device if it is not in the location where the function is looking. It is essentially an overly complicated-looking file not found error message. What makes this problem particularly difficult is that it is not easy to duplicate. This is not a problem with your code, but in an external file that is not where your code expects it to be.
Explanation of the R error
This problem occurs when using the ggplot function and it calls a font that is not where it is supposed to be. One thing that can make this situation particularly troublesome is that it is possible that the font has somehow been moved. If this is the case the error could persist even in new sessions. It is, however, more likely to occur if you are trying to use a new or unusual font. If that is the case, it is going to be even harder to fix because you need to find out what happened to the file.
How to fix the R error
Fixing this problem requires making sure that the file is in the same folder where the function is looking for it. This may require putting the file, preferably by copying it, into the folder that the function is looking for it in. If possible, you can try to redirect the location to where the file is currently found. Finally, you may need to re-download the file and make sure that it is in the proper folder. Unfortunately, this problem has no easy solution because it is going to vary depending upon the situation. Unlike most programming problems this is not a simple matter of showing somebody else your code so that they can see the problem. It is likely that it will run on their computer.
This is a particularly annoying error message because unlike most, it is not an issue with your code or even your data. The difficulty arises because for one reason or another a font file is not where it is expected to be. Furthermore, there is no easy solution to this issue because it has as many solutions as it does causes.