fix(web): guard LLM node model_selector against persisted null (#41707)

web/app/components/workflow/nodes/llm/__tests__/utils.spec.ts

@@ -1,4 +1,8 @@
-import type { EnvironmentVariable, ModelConfig } from '@/app/components/workflow/types'
+import type {
+  EnvironmentVariable,
+  ModelConfig,
+  ValueSelector,
+} from '@/app/components/workflow/types'
 import { AppModeEnum } from '@/types/app'
 import {
   getLLMEnvironmentModel,
@@ -160,5 +164,14 @@ describe('llm utils', () => {
       expect(isEnvironmentModelSource(selector)).toBe(false)
       expect(resolveLLMNodeModel(model, selector, environmentVariables)).toBe(model)
     })
+
+    it('keeps the static model when the persisted selector is null', () => {
+      // A DSL exported from an older/AI-generated workflow can persist `model_selector: null`
+      // instead of omitting the key; this must not crash the same way `undefined` doesn't.
+      const selector = null as unknown as ValueSelector
+
+      expect(isEnvironmentModelSource(selector)).toBe(false)
+      expect(resolveLLMNodeModel(model, selector, environmentVariables)).toBe(model)
+    })
   })
 })

web/app/components/workflow/nodes/llm/utils.ts

@@ -24,7 +24,7 @@ const isLLMEnvironmentVariableValue = (value: unknown): value is LLMEnvironmentV
 }
 
 export const isEnvironmentModelSource = (modelSelector: ValueSelector | undefined) =>
-  modelSelector !== undefined && (modelSelector.length === 0 || modelSelector[0] === 'env')
+  modelSelector != null && (modelSelector.length === 0 || modelSelector[0] === 'env')
 
 export const getLLMEnvironmentModel = (
   modelSelector: ValueSelector | undefined,