[BugFix] Fix NPE (#25032)

Fixes #issue

## What type of PR is this:
- [x] BugFix
- [ ] Feature
- [ ] Enhancement
- [ ] Refactor
- [ ] UT
- [ ] Doc
- [ ] Tool

## Checklist:
- [ ] I have added test cases for my bug fix or my new feature
- [ ] This pr will affect users' behaviors
- [ ] This pr needs user documentation (for new or modified features or
behaviors)
  - [ ] I have added documentation for my new feature or new function

## Bugfix cherry-pick branch check:
- [x] I have checked the version labels which the pr will be
auto-backported to the target branch
  - [ ] 3.1
  - [ ] 3.0
  - [ ] 2.5
  - [x] 2.4
  - [x] 2.3

Signed-off-by: liuyehcf <[email protected]>

fe/fe-core/src/main/java/com/starrocks/qe/Coordinator.java

@@ -2656,7 +2656,7 @@ public void mergeIsomorphicProfiles() {
                 instanceProfile.removeInfoString("Address");
             });
             fragmentProfile.addInfoString("BackendAddresses", String.join(",", backendAddresses));
-            Counter backendNum = fragmentProfile.addCounter("BackendNum", TUnit.UNIT, null);
+            Counter backendNum = fragmentProfile.addCounter("BackendNum", TUnit.UNIT);
             backendNum.setValue(backendAddresses.size());
 
             // Setup number of instance