Josh - it sounds like it's doing what it should be doing.....so maybe the best thing for you is to:
1. Start Condition Statement - if the dropdown is empty then...
2. Generate Report - no filter, just show all records.
3. End Conditional Statement
4. Start Condition Statement - if the dropdown is NOT empty then...
5. Generate Report - filter to show based on the desired dropdown value (like you are doing now)
6. End Conditional Statement
Sorry, it's more steps, but it's the right thing to do.
Paul