Add check to step-12

diff --git a/examples/step-12/step-12.cc b/examples/step-12/step-12.cc
index fcec1e2c1f998d2ffaba5d6cc9ba6f24502d0dd2..70a6bd64c697241a40effff570810537ed754ebc 100644 (file)
--- a/examples/step-12/step-12.cc
+++ b/examples/step-12/step-12.cc
@@ -126,7 +126,9 @@ namespace Step12
     Point<dim> wind_field;
     wind_field(0) = -p(1);
     wind_field(1) = p(0);
-    wind_field /= wind_field.norm();
+
+    if (wind_field.norm() > 1e-10)
+      wind_field /= wind_field.norm();
 
     return wind_field;
   }