fix: typeof bug when passing timeout to dag.get (#3035)

Passing `options` without a `path` to dag.get will throw an error.
```
ipfs.dag.get(cidPath, { timeout: 2000 })

TypeError: Cannot read property 'timeout' of null
```

Cause by the lovely JS issue of `typeof null === 'object'`.

Co-authored-by: Kia Rahimian <kia@tintmail.com>

src/dag/get.js

@@ -16,7 +16,7 @@ module.exports = configure((api, options) => {
   const dagResolve = require('./resolve')(options)
 
   return async (cid, path, options = {}) => {
-    if (typeof path === 'object') {
+    if (path && typeof path === 'object') {
       options = path
       path = null
     }