Add unit test: breaks and labels are different

[selkamand]

Should consider adding a unit test for this:

df <- data.frame(col = c(0, 0, NA, NA, NA, NA, NA, NA, 0, NA))
expect_error(gg1d_plot(df, cols_to_plot="col1"), NA)

Since theres only 1 non-na value (0) an old version of gg1d would throw an error message about breaks and labels being different lengths. We fixed the issue but should add a unit test to catch future instances