Fixed Coverity reported issue.

CID 11830: Uninitialized pointer field (UNINIT_CTOR)
Non-static class member _geometry is not initialized in this constructor nor in any functions that it calls.

src/osgUtil/Simplifier.cpp

@@ -71,7 +71,8 @@ public:
 
 
     EdgeCollapse():
-       _computeErrorMetricUsingLength(false)  {}
+        _geometry(0),
+        _computeErrorMetricUsingLength(false)  {}
         
     ~EdgeCollapse();