When 'Sub-group index' is filled, 'Sub-group header' and/or 'Sub-group footer' has to be filled too.
Explanation:
Normally, articles belonging to an article group are described in one article table, but you can choose to show several article tables under one article group.
When this is the case, each article is assigned to a subgroup.
By means of the Sub-group header and/or footer, the articles within the article group are divided into sub-groups. The Sub-group index column determines the order of the sub-groups. This index only makes sense if sub-groups have been defined using the Sub-group header/footer. If an index is filled in, the Sub-group header and/or footer must be filled in, otherwise there are no subgroups.
Solution:
Please also enter a subgroup header and/or footer in the articles where a subgroup index has been entered.
