Bug 1070825 - Remove the check of not dialing the same number twice
Bug 1065511 - guard against falsey unfilteredStack. r=etienne

* Fallback to using StackManager.getCurrent() in exitToApp
Merge pull request #24323 from dwi2/bug1070825

Bug 1070825 - Remove the check of not dialing the same number twice r=rik
Merge pull request #23967 from sfoster/task-manager-bug-1065511

Bug 1065511 - guard against falsey unfilteredStack. r=etienne