fix: normalise None to empty string for required str fields (company, desc, tags)

Made-with: Cursor

modules/features/trustee/interfaceFeatureTrustee.py

@@ -154,6 +154,10 @@ def _sanitisePositionPayload(data: Dict[str, Any]) -> Dict[str, Any]:
     else:
         safeData["documentType"] = None
 
+    for requiredStrField in ("company", "desc", "tags"):
+        val = safeData.get(requiredStrField)
+        safeData[requiredStrField] = str(val).strip() if val is not None else ""
+
     for strField in ("payeeIban", "payeeName", "payeeBic", "paymentReference"):
         val = safeData.get(strField)
         if val: