fix(devtools-kit): guard state editor against undefined path traversal

packages/devtools-kit/__tests__/component/editor.test.ts

@@ -89,6 +89,21 @@ describe('editor: StateEditor.set', () => {
     })
   })
 
+  describe('editComponentState: non-existing path should not throw', () => {
+    // https://github.com/vuejs/devtools/issues/906
+    it('does not throw when the path points to an undefined value', () => {
+      const target = { foo: 'bar' }
+      const state = { newKey: '', type: '', value: 'baz' }
+      const defaultCallback = stateEditor.createDefaultSetCallback(state)
+      // `bar` does not exist on `target`, so traversal would previously hit
+      // `undefined[field]` and throw a TypeError.
+      expect(() => {
+        stateEditor.set(target, 'bar.baz', 'qux', defaultCallback)
+      }).not.toThrow()
+      expect(target).toEqual({ foo: 'bar' })
+    })
+  })
+
   describe('editComponentState: array', () => {
     it('modify value', () => {
       const target = ['foo', 'bar']

packages/devtools-kit/src/core/component/state/editor.ts

@@ -28,8 +28,15 @@ export class StateEditor {
       else object = object[section] as Recordable
       if (this.refEditor.isRef(object))
         object = this.refEditor.get(object)
+      // The path may not exist on the object (e.g. when editing a Pinia store
+      // from the component inspector). Stop instead of throwing a TypeError
+      // on `undefined[field]`.
+      if (object == null)
+        return
     }
     const field = sections[0]
+    if (object == null)
+      return
     const item = this.refEditor.get(object)[field]
     if (cb) {
       cb(object, field, value)