STYLE: Do not Fill empty local variables in itkMeshIOTestHelper.h

An instance of `itk::Array`, `itk::VariableLengthVector`, or
`itk::VariableSizeMatrix` is empty, when it is just default-constructed. An
attempt to `Fill` such an empty object has no effect.

- Follow-up to pull request InsightSoftwareConsortium#4898
"Do not `Fill` default-constructed empty local variables in tests"

Modules/IO/MeshBase/include/itkMeshIOTestHelper.h

@@ -250,8 +250,7 @@ TestBaseClassMethodsMeshIO(typename TMeshIO::Pointer meshIO)
 
   using ArrayPixelType = itk::Array<FloatType>;
 
-  ArrayPixelType arrayPixelValue;
-  arrayPixelValue.Fill(1.0);
+  ArrayPixelType arrayPixelValue{};
   usePointPixel = true;
   meshIO->SetPixelType(arrayPixelValue, usePointPixel);
   LOCAL_ITK_TEST_SET_GET_VALUE(arrayPixelValue.Size(), meshIO->GetNumberOfPointPixelComponents());
@@ -269,8 +268,7 @@ TestBaseClassMethodsMeshIO(typename TMeshIO::Pointer meshIO)
 
   using VariableLengthVectorPixelType = itk::VariableLengthVector<FloatType>;
 
-  VariableLengthVectorPixelType variableLengthVectorValue;
-  variableLengthVectorValue.Fill(1.0);
+  VariableLengthVectorPixelType variableLengthVectorValue{};
   usePointPixel = true;
   meshIO->SetPixelType(variableLengthVectorValue, usePointPixel);
   LOCAL_ITK_TEST_SET_GET_VALUE(variableLengthVectorValue.Size(), meshIO->GetNumberOfPointPixelComponents());
@@ -288,8 +286,7 @@ TestBaseClassMethodsMeshIO(typename TMeshIO::Pointer meshIO)
 
   using VariableSizeMatrixType = itk::VariableSizeMatrix<FloatType>;
 
-  VariableSizeMatrixType matrix;
-  matrix.Fill(1.0);
+  VariableSizeMatrixType matrix{};
   usePointPixel = true;
   meshIO->SetPixelType(matrix, usePointPixel);
   LOCAL_ITK_TEST_SET_GET_VALUE(matrix.Rows() * matrix.Cols(), meshIO->GetNumberOfPointPixelComponents());