explorer() with addEnv=TRUE will not autoload data frames named "a" or "c"

[bzkrouse]

a <- mtcars
b <- iris
c <- airquality

works as expected:

explorer(data=list(a,b, c), addEnv=FALSE)

does not work as expected ("a" and "c" are not loaded):

explorer(addEnv=TRUE)

We believe this is an issue with the package build, as explorer() function works correctly outside of package. This bug also occurs in codebookApp(), where data frames in the R session are auto-loaded into the app.