remove warnings

clang warns with.
```
/ssd/deal-git/source/fe/fe_tools_extrapolate.cc:708:20: warning:
reference cannot be bound to dereferenced null pointer in well-defined
C++ code; comparison may be assumed to always evaluate to true
[-Wtautological-undefined-compare]
```

diff --git a/source/fe/fe_tools_extrapolate.cc b/source/fe/fe_tools_extrapolate.cc
index eb11aa2c541ee1d1663ffe13228727aca9034e4e..8c4970d2e831f426f7864caa29479816d5ed5e43 100755 (executable)
--- a/source/fe/fe_tools_extrapolate.cc
+++ b/source/fe/fe_tools_extrapolate.cc
@@ -576,8 +576,6 @@ namespace FETools
           const FiniteElement<dim,spacedim> &fe            = dealii_cell->get_dof_handler().get_fe();
           const unsigned int                 dofs_per_cell = fe.dofs_per_cell;
 
-          Assert (&fe != 0,
-                  ExcNotInitialized());
           Assert (interpolated_values.size() == dofs_per_cell,
                   ExcDimensionMismatch(interpolated_values.size(), dofs_per_cell));
           Assert (u.size() == dealii_cell->get_dof_handler().n_dofs(),
@@ -705,8 +703,6 @@ namespace FETools
         }
       else
         {
-          Assert (&fe != 0,
-                  ExcNotInitialized());
           Assert (local_values.size() == dofs_per_cell,
                   ExcDimensionMismatch(local_values.size(), dofs_per_cell));
           Assert (u.size() == dealii_cell->get_dof_handler().n_dofs(),
@@ -1149,8 +1145,6 @@ namespace FETools
       const FiniteElement<dim,spacedim> &fe            = dealii_cell->get_dof_handler().get_fe();
       const unsigned int                 dofs_per_cell = fe.dofs_per_cell;
 
-      Assert (&fe != 0, ExcNotInitialized());
-
       CellData  cell_data (dofs_per_cell);
       cell_data.quadrant = p4est_cell;
       cell_data.tree_index = tree_index;