fix(redirectTo): Do not puke when redirectTo returns undefined

Closes angular-ui/ui-router#3117

src/hooks/redirectTo.ts

@@ -17,9 +17,10 @@ const redirectToHook: TransitionHookFn = (trans: Transition) => {
   let redirect = trans.to().redirectTo;
   if (!redirect) return;
 
-  function handleResult(result: any) {
-    let $state = trans.router.stateService;
+  let $state = trans.router.stateService;
 
+  function handleResult(result: any) {
+    if (!result) return;
     if (result instanceof TargetState) return result;
     if (isString(result)) return $state.target(<any> result, trans.params(), trans.options());
     if (result['state'] || result['params'])

src/params/interface.ts

@@ -190,7 +190,6 @@ export interface ParamDeclaration {
    */
   squash: (boolean|string);
   /**
-   * @hidden
    * @internalapi
    *
    * An array of [[Replace]] objects.
@@ -199,13 +198,13 @@ export interface ParamDeclaration {
    * or empty string `""`.  If the transition is started, and the parameter value is equal to one of the "to"
    * values, then the parameter value is replaced with the "from" value.
    *
-   * @example
-   * ```
-   *
+   * #### Example:
+   * ```js
    * replace: [
    *   { from: undefined, to: null },
    *   { from: "", to: null }
    * ]
+   * ```
    */
   replace: Replace[];
   /**

test/hooksSpec.ts

@@ -106,6 +106,17 @@ describe("hooks", () => {
       })
     })
 
+    // Test for #3117
+    it("should not redirect if the redirectTo: function returns undefined", (done) => {
+      find(states, s => s.name === 'A').redirectTo = function() {};
+      init();
+
+      $state.go('A').then(() => {
+        expect(router.globals.current.name).toBe('A');
+        done()
+      })
+    })
+
     it("should not redirect if the redirectTo: function returns something other than a string, { state, params}, TargetState (or promise for)", (done) => {
       find(states, s => s.name === 'A').redirectTo = () => new Promise((resolve) => {
         setTimeout(() => resolve(12345), 50)