Strip srcref attribute from constructor expression (#6472)

Author: yjunechoe

R/layer.R

@@ -181,6 +181,7 @@ layer <- function(geom = NULL, stat = NULL,
   geom <- set_draw_key(geom, key_glyph %||% params$key_glyph)
 
   fr_call <- layer_class$constructor %||% frame_call(call_env) %||% current_call()
+  attr(fr_call, "srcref") <- NULL
 
   ggproto("LayerInstance", layer_class,
     constructor = fr_call,