Saiku error with the last pentaho mondrian version

[omejiasq]

Is this a bug report?

Yes

Environment

1. java -version:
   1.8.0_144
2. node -v (If you use Node.js proxy for Saiku):
3. npm -v (If you use Node.js proxy for Saiku):
4. yarn --version (If you use Node.js proxy for Saiku and if you use Yarn):

Then, specify:

1. Operating system:
   Windonws 10
2. Browser and version (if relevant):
   Google chrome 87.0.4280.14 version
3. Saiku plugin to Pentaho or Saiku Standalone:
   Saiku plugin for pentaho 8.3
4. Saiku CE or Saiku EE:
   Saiku CE
5. Saiku version:
   Saiku 3.0 plugin for pentaho 8.3

Steps to Reproduce

(Write your steps here:)

1. Open google chrome
2. Open pentaho 8 or 9
3. Open saiku
4. Open the filter window on a selected dimension level

Expected Behavior

It should show the level data of the selected dimension. But it shows the filter window blank

Actual Behavior

When opening the saiku filter window of a selected dimension level, it shows this filter window blank. When opening google chrome development tools it shows the following error:
jquery.min.js:6 GET http://localhost:8080/pentaho/plugin/saiku/api/api/query/7949AE50-9D81-3E4A-8E4A-AD834B14F366/result/metadata/hierarchies/%5BRegion%5D/levels/Region?result=true&searchlimit=3000&_=1610208345739 500
send @ jquery.min.js:6
ajax @ jquery.min.js:6
Backbone.sync @ saiku.min.js:558
sync @ backbone.js:286
fetch @ backbone.js:440
handle @ saiku.min.js:466
gett @ saiku.min.js:465
get_members @ saiku.min.js:125
initialize @ saiku.min.js:124
Backbone.View @ backbone.js:1001
child @ backbone.js:1566
child @ backbone.js:1566
selections @ saiku.min.js:320
dispatch @ jquery.min.js:5
v.handle @ jquery.min.js:5
saiku.min.js:557 Error performing GET on ../../plugin/saiku/api/api/query/7949AE50-9D81-3E4A-8E4A-AD834B14F366/result/metadata/hierarchies/%5BRegion%5D/levels/Region