Special case for 0 rows and 0 aesthetics.

Fixes #1451

Author: hadley

NEWS.md

@@ -1,5 +1,8 @@
 # ggplot2 2.0.0.9000
 
+* Eliminate spurious warning if you have a layer with no data and no aesthetics
+  (#1451).
+
 * `position = "nudge"` now works (although it doesn't do anything useful)
   (#1428).
 

R/layer.r

@@ -134,7 +134,11 @@ Layer <- ggproto("Layer", NULL,
     n <- nrow(data)
     if (n == 0) {
       # No data, so look at longest evaluated aesthetic
-      n <- max(vapply(evaled, length, integer(1)))
+      if (length(evaled) == 0) {
+        n <- 0
+      } else {
+        n <- max(vapply(evaled, length, integer(1)))
+      }
     }
     check_aesthetics(evaled, n)