Core/Misc: Fix some static analysis issues

Fix some static analysis issues about:
- uninitialized values, most of which are false positives, always initialized before being accessed
- unchecked return values
- dead code never executed
- bad formatting leading to wrong behavior

Please ensure EventMap is never used with event id set to 0 or those events will never execute.

src/server/shared/Database/QueryHolder.cpp

@@ -89,10 +89,9 @@ QueryResult SQLQueryHolder::GetResult(size_t index)
     if (index < m_queries.size())
     {
         ResultSet* result = m_queries[index].second.qresult;
-        if (!result || !result->GetRowCount())
+        if (!result || !result->GetRowCount() || !result->NextRow())
             return QueryResult(NULL);
 
-        result->NextRow();
         return QueryResult(result);
     }
     else