BUG: Pointer to temporary variable needs resetting to null.

When the pointer to the local variable persists outside of
the local function.  When the local variable goes out of
scope the mutable class variable should be set to nullptr.

Author: hjmjohnson

Modules/Registration/Metricsv4/include/itkImageToImageMetricv4.hxx

@@ -206,15 +206,15 @@ typename ImageToImageMetricv4<TFixedImage, TMovingImage, TVirtualImage, TInterna
 {
   this->m_ComputeDerivative = false;
 
-  DerivativeType derivative;
-  this->m_DerivativeResult = &derivative;
+  DerivativeType local_derivative;
+  this->m_DerivativeResult = &local_derivative;
   this->InitializeForIteration();
 
   // Do the threaded processing using the appropriate
   // GetValueAndDerivativeThreader. Results get written to
   // member vars.
   this->GetValueAndDerivativeExecute();
-
+  this->m_DerivativeResult = nullptr; // Pointer to temporary local_derivative is invalid after function return
   return this->m_Value;
 }