Fix ambiguous operations when C++11 Urho3D features are enabled by using WeakPtr default constructor instead.

Source/Urho3D/Graphics/View.cpp

@@ -297,7 +297,6 @@ View::View(Context* context) :
     octree_(0),
     cullCamera_(0),
     camera_(0),
-    sourceView_(0),
     cameraZone_(0),
     farClipZone_(0),
     occlusionBuffer_(0),

Source/Urho3D/Scene/SplinePath.cpp

@@ -41,7 +41,6 @@ SplinePath::SplinePath(Context* context) :
     traveled_(0.f),
     length_(0.f),
     dirty_(false),
-    controlledNode_(NULL),
     controlledIdAttr_(0)
 {
     UpdateNodeIds();