From Micheal Gronager, fix to osg::Quat::getRotate(..) to handle zero rotations.

Port of Sequence to subclass directly from osg::Group.

src/osg/Sequence.cpp

@@ -1,4 +1,5 @@
 #include <osg/Sequence>
+#include <osg/Notify>
 
 using namespace osg;
 
@@ -177,6 +178,10 @@ void Sequence::traverse(NodeVisitor& nv)
             }
             setValue(sw);
         }
+        else
+        {
+            osg::notify(osg::WARN) << "osg::Sequence::traverse(NodeVisitor&) requires a valid FrameStamp to function, sequence not updated.\n";
+        }
     }
     
     // now do the traversal