What/Where is the issue ?

In bar chart report, trying to set a bucket size after grouping by variable is failing. 

Environment: C7/ C8SaaS/ C8SM

Optimize version : SNAPSHOT

Steps to reproduce:

• Preconditions:
• Steps:

1. Create a report Flow Node - Group by Flow Node and Variable
2. Go to configuration options 
3. Enable bucket size setting 

Observed behavior:

Report is failing. 

Expected behavior:

Bucket size should set as expected. 

Additional Information: