Fix fromObject when object is undefined

In atom@1.20.0 there is an unrecoverable error occurring when parameter `object` is undefined.

```
Uncaught (in promise) TypeError: Cannot read property 'start' of undefined
    at Function.module.exports.Range.fromObject (/Applications/Atom.app/Contents/Resources/app/node_modules/text-buffer/lib/range.js:33:37)
    at Function.module.exports.MarkerLayer.deserializeSnapshot (/Applications/Atom.app/Contents/Resources/app/node_modules/text-buffer/lib/marker-layer.js:39:57)
    at History.module.exports.History.deserializeStack (/Applications/Atom.app/Contents/Resources/app/node_modules/text-buffer/lib/history.js:427:60)
    at History.module.exports.History.deserialize (/Applications/Atom.app/Contents/Resources/app/node_modules/text-buffer/lib/history.js:361:35)
    at /Applications/Atom.app/Contents/Resources/app/node_modules/text-buffer/lib/text-buffer.js:264:30
```

Author: bstream

src/range.coffee

@@ -45,7 +45,7 @@ class Range
     else if object instanceof this
       if copy then object.copy() else object
     else
-      new this(object.start, object.end)
+      if object != null then new this(object.start, object.end) else new this()
 
   # Returns a range based on an optional starting point and the given text. If
   # no starting point is given it will be assumed to be [0, 0].