Fixed bug in vtkCachingInterpolatedVelocityField.

vtkCachingInterpolatedVelocityField was passing -1 to GetCell() the
first time around. Since GetCell() expects a valid cell id, this was
causing all kinds of issues. Also, it was not calling FindCell()
the right way - it was always passing -1 for the cell id causing it
to use the locator every time. Fixed both.

Change-Id: I8025666e046f4b39d7b43d5c3b71f69f763b20ef

Filters/FlowPaths/vtkCachingInterpolatedVelocityField.cxx

@@ -286,9 +286,14 @@ int vtkCachingInterpolatedVelocityField::FunctionValues(
     }
   else
     {
-    data->DataSet->GetCell(this->LastCellId, this->TempCell);
+    vtkGenericCell* tmpCell = 0;
+    if (this->LastCellId >= 0)
+      {
+      data->DataSet->GetCell(this->LastCellId, this->TempCell);
+      tmpCell = this->TempCell;
+      }
     this->LastCellId =
-      data->DataSet->FindCell(x, this->TempCell, data->Cell, -1,
+      data->DataSet->FindCell(x, tmpCell, data->Cell, this->LastCellId,
       data->Tolerance, subId, data->PCoords, &this->Weights[0]);
     if (this->LastCellId != -1)
       {