No ticks no space

[teunbrand]

This PR aims to fix #6069.

Briefly, this PR sets ticks lengths to 0 if the corresponding tick is blank.

Examples from #4722. Current situation:

library(ggplot2)

ggplot(mpg, aes(displ, cty)) +
  geom_point() +
  theme(
    axis.ticks = element_blank(),
    axis.ticks.length = unit(2, "cm")
  )

With this PR:

devtools::load_all("~/packages/ggplot2")
#> ℹ Loading ggplot2

ggplot(mpg, aes(displ, cty)) +
  geom_point() +
  theme(
    axis.ticks = element_blank(),
    axis.ticks.length = unit(2, "cm")
  )

^{Created on 2024-09-03 with reprex v2.1.1}