Editor code: tidy up BOOLs,NULLs and overrides pt5. (#2876)

A few 'typedefs' replaced by 'using's
This shouldn't have any functional changes at all, just c++17 modernization
It's a part 5 of a split #2847

Signed-off-by: Nemerle <nemerle5+git@gmail.com>

Co-authored-by: Nemerle <nemerle5+git@gmail.com>

Code/Editor/ErrorReport.cpp

@@ -136,11 +136,11 @@ void CErrorReport::ReportError(CErrorRecord& err)
     }
     else
     {
-        if (err.pObject == NULL && m_pObject != NULL)
+        if (err.pObject == nullptr && m_pObject != nullptr)
         {
             err.pObject = m_pObject;
         }
-        else if (err.pItem == NULL && m_pItem != NULL)
+        else if (err.pItem == nullptr && m_pItem != nullptr)
         {
             err.pItem = m_pItem;
         }