be more thorough with truncating label lists

Author: teunbrand

R/layer.R

@@ -974,10 +974,8 @@ normalise_label <- function(label) {
   if (obj_is_list(label)) {
     # Ensure that each element in the list has length 1
     label[lengths(label) == 0] <- ""
-    # Don't mess with call/formula
-    if (!is.call(label[[1]])) {
-      label[] <- lapply(label, `[`, 1)
-    }
+    truncate <- !vapply(label, is.call, logical(1)) # Don't mess with call/formula
+    label[truncate] <- lapply(label[truncate], `[`, 1)
   }
   if (is.expression(label)) {
     # Classed expressions, when converted to lists, retain their class.