Work around null-dereference bug in some versions of asymptote.

See
  http://sourceforge.net/tracker/?func=detail&aid=3292023&group_id=120000&atid=685683
for details on the bug.

diff --git a/tex/src/figures/schematic/base_afm.asy b/tex/src/figures/schematic/base_afm.asy
index e73f1275128d02cd383c17952b5495e187c150b9..935a59ca80604134dfe66f6b0898596b0920d2d4 100644 (file)
--- a/tex/src/figures/schematic/base_afm.asy
+++ b/tex/src/figures/schematic/base_afm.asy
@@ -154,7 +154,7 @@ struct Substrate {
       pair arrow_center = piezo_bot + (0, arrow_length/2 + 2pt);
       arrow(b=arrow_center + dir*arrow_length/2, dir=-dir,
            length=this.piezo_height/3, Arrow(size=8pt),
-           margin=NoMargin);
+           margin=NoMargin, L="");
     }
   }
 
@@ -239,8 +239,8 @@ void distance(Label L, pair start, pair end) {
   pair label_size = 1.2 * (max(picL)-min(picL));
   real arrow_length = length(end-start)/2 - label_size.y;
   if (arrow_length > 4pt) {
-    arrow(b=start, dir=u, length=arrow_length, Arrow(size=4pt));
-    arrow(b=end, dir=-u, length=arrow_length, Arrow(size=4pt));
+    arrow(b=start, dir=u, length=arrow_length, Arrow(size=4pt), L="");
+    arrow(b=end, dir=-u, length=arrow_length, Arrow(size=4pt), L="");
   }
   label(L, center);
 }