fixed failing test case, so we can use the browser API from JVM code and at least have an empty document to play with

libraries/stdlib/src/kotlin/browser/Properties.kt

@@ -1,7 +1,7 @@
 package kotlin.browser
 
-import org.w3c.dom.Document
 import js.native
+import org.w3c.dom.Document
 
 private var _document: Document? = null
 
@@ -9,7 +9,13 @@ private var _document: Document? = null
  * Provides access to the current active browsers DOM for the currently visible page.
  */
 native public var document: Document
- get() = _document!!
+    get() {
- set(value) {
+        // Note this code is only executed on the JVM
-     _document = value
+        val answer = _document
- }
+        return if (answer == null) {
+            kotlin.dom.createDocument()
+        } else answer
+    }
+    set(value) {
+        _document = value
+    }