diff --git a/lib/galaxy/tools/parameters/basic.py b/lib/galaxy/tools/parameters/basic.py
index 91d07badae1..3c70f0800da 100644
--- a/lib/galaxy/tools/parameters/basic.py
+++ b/lib/galaxy/tools/parameters/basic.py
@@ -2215,6 +2215,12 @@ class DataToolParameter(BaseDataToolParameter):
                     ),
                 ):
                     rval.append(single_value)
+                elif single_value in (None, "None", ""):
+                    # An unset optional data input (e.g. connected to a multiple
+                    # data parameter) arrives as a null list element. Tolerate it
+                    # as "no dataset" the way to_python() filters it, rather than
+                    # treating null as a malformed id (regression from #22617).
+                    continue
                 else:
                     pk = _decode_dataset_id(single_value, trans.security, self.name)
                     rval.append(trans.sa_session.get(HistoryDatasetAssociation, pk))
diff --git a/test/unit/app/tools/test_data_parameters.py b/test/unit/app/tools/test_data_parameters.py
index 3acf51d77e5..9beefa850d4 100644
--- a/test/unit/app/tools/test_data_parameters.py
+++ b/test/unit/app/tools/test_data_parameters.py
@@ -45,6 +45,16 @@ class TestDataToolParameter(BaseParameterTestCase):
         with pytest.raises(ParameterValueError, match="invalid dataset id"):
             self.param.from_json("not-an-id", self.trans)
 
+    def test_from_json_multi_tolerates_none(self):
+        # An unset optional data input connected to a multiple data parameter
+        # arrives as a null list element; it must be filtered out rather than
+        # rejected as a malformed id (regression from #22617, surfaced as a
+        # workflow run erroring on an unset optional data input).
+        self.multiple = True
+        self.optional = True
+        assert self.param.from_json([None], self.trans) == []
+        assert self.param.from_json(["None"], self.trans) == []
+
     def test_field_filter_on_types(self):
         hda1 = MockHistoryDatasetAssociation(name="hda1", id=1)
         hda2 = MockHistoryDatasetAssociation(name="hda2", id=2)