Fix memory read error in MDHistoWorkspaceIterator & test

The skipping policy was being applied even if the iterator had
reached the last element causing the skipping policy check to
access an array out of bounds.
Refs #11512

Code/Mantid/Framework/DataObjects/src/MDHistoWorkspaceIterator.cpp

@@ -237,12 +237,14 @@ bool MDHistoWorkspaceIterator::next() {
   } else {
     ++m_pos;
   }
-  // Keep calling next if the current position is masked.
   bool ret = m_pos < m_max;
-  while (m_skippingPolicy->keepGoing()) {
-    ret = this->next();
-    if (!ret)
-      break;
+  if(ret) {
+    // Keep calling next if the current position is masked and still valid.
+    while (m_skippingPolicy->keepGoing()) {
+      ret = this->next();
+      if (!ret)
+        break;
+    }
   }
   // Go through every point;
   return ret;

Code/Mantid/Framework/DataObjects/test/MDHistoWorkspaceIteratorTest.h

@@ -8,14 +8,14 @@
 #include "MantidDataObjects/MDHistoWorkspaceIterator.h"
 #include "MantidTestHelpers/MDEventsTestHelper.h"
 #include <cxxtest/TestSuite.h>
-#include <iomanip>
-#include <iostream>
 #include "MantidKernel/VMD.h"
 #include "MantidGeometry/MDGeometry/MDImplicitFunction.h"
 #include "MantidGeometry/MDGeometry/MDPlane.h"
 #include <boost/assign/list_of.hpp>
 #include <boost/function.hpp>
 #include <boost/bind.hpp>
+#include <boost/scoped_ptr.hpp>
+
 
 using namespace Mantid;
 using namespace Mantid::DataObjects;
@@ -67,9 +67,10 @@ class MDHistoWorkspaceIteratorTest: public CxxTest::TestSuite
   void do_test_iterator(size_t nd, size_t numPoints)
   {
     MDHistoWorkspace_sptr ws = MDEventsTestHelper::makeFakeMDHistoWorkspace(1.0, nd, 10);
-    for (size_t i = 0; i < numPoints; i++)
+    for (size_t i = 0; i < numPoints; i++) {
       ws->setSignalAt(i, double(i));
-    MDHistoWorkspaceIterator * it = new MDHistoWorkspaceIterator(ws);
+    }
+    boost::scoped_ptr<MDHistoWorkspaceIterator> it(new MDHistoWorkspaceIterator(ws));
     TSM_ASSERT( "This iterator is valid at the start.", it->valid());
     size_t i = 0;
 
@@ -90,10 +91,10 @@ class MDHistoWorkspaceIteratorTest: public CxxTest::TestSuite
     {
       TS_ASSERT_DELTA( it->getNormalizedSignal(), double(i) / 1.0, 1e-5);
       TS_ASSERT_DELTA( it->getNormalizedError(), 1.0, 1e-5);
-      coord_t * vertexes;
       size_t numVertices;
-      vertexes = it->getVertexesArray(numVertices);
-      TS_ASSERT( vertexes);
+      coord_t *vertexes = it->getVertexesArray(numVertices);
+      TS_ASSERT(vertexes);
+      delete [] vertexes;
       TS_ASSERT_EQUALS( it->getNumEvents(), 1);
       TS_ASSERT_EQUALS( it->getInnerDetectorID(0), 0);
       TS_ASSERT_EQUALS( it->getInnerRunIndex(0), 0);