Fix Itanium VFT analysis crashing when possible VFT at section start boundary

The vft will have a few fields above it, we did not verify that when we read those fields that they were readable.

Fixes #6694

Author: emesare

plugins/rtti/itanium.cpp

@@ -768,6 +768,8 @@ void ItaniumRTTIProcessor::ProcessVFT()
                 continue;
             // Verify that there is two field sized values above the type info pointer
             optReader.Seek(ref - ArchFieldSize(m_view) * 2);
+            if (!m_view->IsValidOffset(optReader.GetOffset()))
+                continue;
             auto beforeTypeInfoRef = optReader.ReadPointer();
             if (m_view->IsValidOffset(beforeTypeInfoRef))
                 continue;