backend: throw error if name is empty for PUT /api/workflows/{id}

This is handled at the frontend in the editor to prevent this,
but still add additional check in backend

client/src/components/Workflow/Editor/Index.vue

@@ -617,13 +617,12 @@ export default {
                     );
                 }
             } catch (e) {
-                this.onWorkflowError("Creating workflow failed"),
-                    e || "Please contact an administrator.",
-                    {
-                        Ok: () => {
-                            this.hideModal();
-                        },
-                    };
+                const response = e.response.data.err_msg || e || "Please contact an administrator.";
+                this.onWorkflowError("Creating workflow failed", response, {
+                    Ok: () => {
+                        this.hideModal();
+                    },
+                });
             }
         },
         nameValidate() {

lib/galaxy/webapps/galaxy/api/workflows.py

@@ -472,6 +472,8 @@ def update(self, trans: GalaxyWebTransaction, id, payload, **kwds):
             new_workflow_name = workflow_dict.get("name")
             old_workflow = stored_workflow.latest_workflow
             name_updated = new_workflow_name and new_workflow_name != stored_workflow.name
+            if not name_updated:
+                raise exceptions.MessageException("Please provide a workflow name.")
             steps_updated = "steps" in workflow_dict
             if name_updated and not steps_updated:
                 sanitized_name = sanitize_html(new_workflow_name or old_workflow.name)