Fix browsing of tables without rowid

Browsing WITHOUT ROWID tables was broken since a couple of commits. An
error message would be printed to the console and all cells would stay
empty. This is fixed by this commit.

src/sqlitetablemodel.h

@@ -86,6 +86,7 @@ private:
 
     QString m_sQuery;
     QString m_sTable;
+    QString m_sRowidColumn;
     QString m_pseudoPk;
     int m_iSortColumn;
     QString m_sSortOrder;