fix($browser): don't crash if history.state access causes error in IE

Reportedly, MSIE can throw under certain conditions when fetching this attribute.
We don't have a reliable reproduction for this but it doesn't do any real harm
to wrap access to this variable in a try-catch block.

Fixes #10367
Closes #10369

Author: caitp

src/ng/browser.js

@@ -233,11 +233,19 @@ function Browser(window, document, $log, $sniffer) {
     fireUrlChange();
   }
 
+  function getCurrentState() {
+    try {
+      return history.state;
+    } catch (e) {
+      // MSIE can reportedly throw when there is no state (UNCONFIRMED).
+    }
+  }
+
   // This variable should be used *only* inside the cacheState function.
   var lastCachedState = null;
   function cacheState() {
     // This should be the only place in $browser where `history.state` is read.
-    cachedState = window.history.state;
+    cachedState = getCurrentState();
     cachedState = isUndefined(cachedState) ? null : cachedState;
 
     // Prevent callbacks fo fire twice if both hashchange & popstate were fired.