Query groups return no rows, but I need to calculate on all groups

 I have a report where I go through the Bill of Materials and for each item,  I have a group querying the on-hand quantity, another group querying open purchase orders, another group querying what we will be making with wip jobs, and another group querying what may be allocated to be used on wip jobs.

In the last group, I also try to calculate what's onhand minus what may be allocated to wip jobs to show what's left.

I have the groups all linked by item id.

The issue I am having is that if the on-hand query returns no rows, it is "breaking" the links to the rest of the groups.  It appears then that the other