diff -r 509d90004912 source/core/math/spline.cpp
--- a/source/core/math/spline.cpp	Fri Sep 18 19:12:10 2015 +0200
+++ b/source/core/math/spline.cpp	Sun Oct 04 10:09:19 2015 +0200
@@ -670,7 +670,26 @@
     /* If p is already in spline, replace */
     /* The clause after the || is needed because findt returns sp->Splin
eEntries.size()
      * if p is greater than OR EQUAL TO the highest par in the spline */

-    if(!sp->SplineEntries.empty() && ((sp->SplineEntries[i].par == p
) || (i == sp->SplineEntries.size() && sp->SplineEntries[i-1].par =
= p)))
+    bool replace= false;
+    size_t splineSize = sp->SplineEntries.size();// might be needed mo
re than once, so compute and store 
+    if (splineSize) // not empty
+    {
+      if (i==splineSize)
+      {// special case, i would be out of bound
+	if (sp->SplineEntries[i-1].par == p)
+	{
+	  replace = true;
+	}
+      }
+      else
+      {// normal branch, i is inbound
+	if (sp->SplineEntries[i].par == p)
+	{
+	  replace = true;
+	}
+      }
+    }
+    if (replace)
     {
         for(k=0; k<5; k++)
             sp->SplineEntries[i].vec[k] = v[k];