Fix loadFinished signal in case of interrupting error page loading

If the error page loading is interrupted by loading of another page the
signals of the second page should not be suppressed.

Change-Id: I537daabf80ffed005acaaf2a6019e52a3250c523
Reviewed-by: Andras Becsi <andras.becsi@digia.com>
Reviewed-by: Zeno Albisser <zeno.albisser@digia.com>
Reviewed-by: Adam Kallai <kadam@inf.u-szeged.hu>