Core/DBLayer: Fix a memory leak in Field class, properly clear buffer before repopulating it.

Fixes many issues (from wrong subnames on NPCs to absent GO/Creature spawns)
Thanks to Rat for helping find the issue

--HG--
branch : trunk

src/server/shared/Database/QueryResult.cpp

@@ -162,7 +162,7 @@ bool ResultSet::NextRow()
     }
 
     for (uint32 i = 0; i < m_fieldCount; i++)
-        m_currentRow[i].SetStructuredValue(row[i], m_fields[i].type, Field::SizeForType(&m_fields[i]));
+        m_currentRow[i].SetStructuredValue(row[i], m_fields[i].type);
 
     return true;
 }