We are seeing the same error in webi reports but we found the workaround here.
We need to run the report in Applet mode in Launch pad.
Preferences --> Web Intelligence-->Select Applet mode in both "View" and "Modify" sections.
If this is not works then try the below one as well:
Please go to design mode then edit the query and see the sample data in the data preview pane and run the queries again and save the report.
Now open the report and see the result.
@Viswanadh Chaudhary.