fix: add defensive guard for invalid modelType in findProvidersWithFallback

- Early return undefined for null/undefined/non-string inputs
- Prevents potential runtime errors from .split() on invalid types
- Add tests for invalid input handling

Amp-Thread-ID: https://ampcode.com/threads/T-019c0849-5650-7060-b4bd-23ef0c8dfa39
Co-authored-by: Amp <amp@ampcode.com>

src/stores/modelToNodeStore.test.ts

@@ -539,5 +539,16 @@ describe('useModelToNodeStore', () => {
       expect(modelToNodeStore.getNodeProvider('')).toBeUndefined()
       expect(modelToNodeStore.getAllNodeProviders('')).toEqual([])
     })
+
+    it('should handle invalid input types gracefully', () => {
+      const modelToNodeStore = useModelToNodeStore()
+      modelToNodeStore.registerDefaults()
+
+      expect(modelToNodeStore.getNodeProvider(null as any)).toBeUndefined()
+      expect(modelToNodeStore.getNodeProvider(undefined as any)).toBeUndefined()
+      expect(modelToNodeStore.getNodeProvider(123 as any)).toBeUndefined()
+      expect(modelToNodeStore.getAllNodeProviders(null as any)).toEqual([])
+      expect(modelToNodeStore.getAllNodeProviders(undefined as any)).toEqual([])
+    })
   })
 })

src/stores/modelToNodeStore.ts

@@ -81,6 +81,10 @@ export const useModelToNodeStore = defineStore('modelToNode', () => {
   function findProvidersWithFallback(
     modelType: string
   ): ModelNodeProvider[] | undefined {
+    if (!modelType || typeof modelType !== 'string') {
+      return undefined
+    }
+
     const exactMatch = modelToNodeMap.value[modelType]
     if (exactMatch && exactMatch.length > 0) return exactMatch