MSPileup monitoringTask fail to track containers without any wmcore_transferor rules
**Impact of the bug**
MSPileup

**Describe the bug**
Hasan pointed out to this RelVal pileup:
```
/RelValMinBias_14TeV/CMSSW_13_1_0_pre2-131X_mcRun4_realistic_v2_2026D95noPU-v2/GEN-SIM
```

which is supposed to have 1 `wmcore_transferor` rule locking it at T2_CH_CERN, accessible through (but also copied in [1]):
https://cmsweb.cern.ch/ms-pileup/data/pileup?pileupName=/RelValMinBias_14TeV/CMSSW_13_1_0_pre2-131X_mcRun4_realistic_v2_2026D95noPU-v2/GEN-SIM

It turns out that that rule `4650a485fe3f44258f5aedb60139a5cb` does not even exist in Rucio; and MSPileup is not taking any action on the pileup either.

Problem seems to be in the `monitoringTask` which iterates through all the `wmcore_transferor`, however, it does not account for the case where no rules are found in Rucio:
https://github.com/dmwm/WMCore/blob/master/src/python/WMCore/MicroService/MSPileup/MSPileupTasks.py#L259

**How to reproduce it**
Have a pileup configuration with existent rules, then delete all wmcore_transferor rules.

**Expected behavior**
If a pileup is active (active=True), it has expected RSEs in the configuration, but no rules in Rucio are found; it is expected that MSPileup will:
* cleanup the `currentRSEs` property
* and cleanup the `ruleIds` property.

With that, the `activeTask` will pick it up and make the relevant data placement.

**Additional context and error message**
[1]
```
{"result": [
 {
  "pileupName": "/RelValMinBias_14TeV/CMSSW_13_1_0_pre2-131X_mcRun4_realistic_v2_2026D95noPU-v2/GEN-SIM",
  "pileupType": "premix",
  "insertTime": 1681914426,
  "lastUpdateTime": 1682596591,
  "expectedRSEs": [
    "T2_CH_CERN"
  ],
  "currentRSEs": [
    "T2_CH_CERN"
  ],
  "fullReplicas": 1,
  "campaigns": [],
  "containerFraction": 1.0,
  "replicationGrouping": "ALL",
  "activatedOn": 1682596591,
  "deactivatedOn": 1681914426,
  "active": true,
  "pileupSize": 33060714720,
  "ruleIds": [
    "4650a485fe3f44258f5aedb60139a5cb"
  ]
}]}
```
diff --git a/src/python/WMCore/MicroService/MSPileup/MSPileupTasks.py b/src/python/WMCore/MicroService/MSPileup/MSPileupTasks.py
index cca610ec4..7a6a6174e 100644
--- a/src/python/WMCore/MicroService/MSPileup/MSPileupTasks.py
+++ b/src/python/WMCore/MicroService/MSPileup/MSPileupTasks.py
@@ -256,6 +256,15 @@ def monitoringTask(doc, spec):
     rules = rucioClient.listDataRules(pname, **kwargs)
     modify = False
 
+    if not rules:
+        logger.info(f"Did not find any wmcore_transferor rules for container: {pname}.")
+        if not doc['expectedRSEs']:
+            logger.warning(f"Container: {pname} is active but has no expected RSEs.")
+        elif doc['currentRSEs'] or doc['ruleIds']:
+            doc['currentRSEs'].clear()
+            doc['ruleIds'].clear()
+            modify = True
+
     for rdoc in rules:
         rses = rucioClient.evaluateRSEExpression(rdoc['rse_expression'])
         rid = rdoc['id']
['src/python/WMCore/MicroService/MSPileup/MSPileupTasks.py']