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

spec/range-spec.coffee

@@ -4,6 +4,12 @@ describe "Range", ->
   beforeEach ->
     jasmine.addCustomEqualityTester(require("underscore-plus").isEqual)
 
+  describe "::fromObject() when object is falsy", ->
+    it "should not throw", ->
+      expect(-> Range.fromObject(null)).not.toThrow()
+    it "should get default values", ->
+      expect(Range.fromObject(null).toString()).toBe "[(0, 0) - (0, 0)]"
+
   describe "::intersectsWith(other, [exclusive])", ->
     intersectsWith = (range1, range2, exclusive) ->
       range1 = Range.fromObject(range1)

src/range.coffee

@@ -39,7 +39,7 @@ class Range
   #   that are already ranges.˚
   #
   # Returns: A {Range} based on the given object.
-  @fromObject: (object, copy) ->
+  @fromObject: (object = {}, copy) ->
     if Array.isArray(object)
       new this(object[0], object[1])
     else if object instanceof this