Stimulsoft import fix

[GauriSpears]

There were errors importing Stimulsoft templates: "Can't load the report. Object reference not set to an instance of an object".

1. Condition node may be absent. Null-check added.
2. Fixed incorrect order of multiple GroupHeaderBand and GroupFooterBand.
3. Fixed error in CreateGroupFooterBand(GroupHeaderBand groupHeaderBand) caused by GetParentGroupHeaderBand returning null.