Fix blank strip text with multilayered strips (#4384)

* Subset zeroGrobs during strip assembly

* Add news bullet

Author: teunbrand

NEWS.md

@@ -22,6 +22,9 @@
 
 * `stat_bin()`'s computed variable `width` is now documented (#3522).
 
+* Fixed a bug in strip assembly when theme has `strip.text = element_blank()`
+  and plots are faceted with multi-layered strips (@teunbrand, #4384).
+
 * ggplot2 now requires R >= 3.3 (#4247).
 
 * ggplot2 now uses `rlang::check_installed()` to check if a suggested package is

R/labeller.r

@@ -553,7 +553,11 @@ build_strip <- function(label_df, labeller, theme, horizontal) {
 #'
 #' @noRd
 assemble_strips <- function(grobs, theme, horizontal = TRUE, clip) {
-  if (length(grobs) == 0 || is.zero(grobs[[1]])) return(grobs)
+  if (length(grobs) == 0 || is.zero(grobs[[1]])) {
+    # Subsets matrix of zeroGrobs to correct length (#4050)
+    grobs <- grobs[seq_len(NROW(grobs))]
+    return(grobs)
+  }
 
   # Add margins to non-titleGrobs so they behave eqivalently
   grobs[] <- lapply(grobs, function(g) {