What is the %||% operator?

I'm trying to create a custom ggplot2 geom by modifying geom_errorbar. The geom_errorbar function uses an operator that I've never seen before %||%, on line 37 here:

does anyone know what it is, and which package define it? Trying to run my custom geom I get the error:

Error in data$width %||% params$width %||% (resolution(data$x, FALSE) *  (from geom_errorbar2.R#40) : 
  could not find function "%||%"
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