vtkArcGridActorPrivate.cxx: vector reserve to vector reserve and init

on line 85 there is an error when tests are run with libc++ hardness mode with the debug setting
on line 82 we reserve space for the vector this does not change n though so when
we access it on line 85 there is an error n=0, to fix this we reserve and initalize the vector

Rendering/Annotation/vtkArcGridActorPrivate.cxx

@@ -79,8 +79,7 @@ void vtkArcGridActorPrivate::BuildGrid(vtkViewport* viewport)
 
   const double totalAngle = vtkMath::RadiansFromDegrees(this->Angle);
 
-  std::vector<vtkIdType> pids;
-  pids.reserve(this->Resolution);
+  std::vector<vtkIdType> pids(this->Resolution);
   for (int arc = 0; arc < nbArcs; arc++)
   {
     pids[0] = polyDataPoints->InsertNextPoint(this->TicksStart->GetPoint(arc));