🐛 bug(path): fix branket key error

Author: kazupon

src/path.js

@@ -194,6 +194,7 @@ function parse (path: Path): ?Array<string> {
       actions[APPEND]()
     } else {
       subPathDepth = 0
+      if (key === undefined) { return false }
       key = formatSubPath(key)
       if (key === false) {
         return false

test/unit/path.test.js

@@ -77,4 +77,16 @@ describe('path', () => {
       assert.strictEqual(path.getPathValue(null, 'a.b'), null)
     })
   })
+
+  describe('Blanket: term', () => {
+    it('should not get null', () => {
+      assert.strictEqual(path.getPathValue({}, 'a.b.c[]'), null)
+    })
+  })
+
+  describe('Blanket: middle', () => {
+    it('should not get null', () => {
+      assert.strictEqual(path.getPathValue({}, 'a.b.c[]d'), null)
+    })
+  })
 })