bug: cancel/finish task before the end of a pomodoro timer throws an exception.

[rchamarthy]

Uncaught Exception:
Error: Command failed: /usr/local/bin/task stop 1
at checkExecSyncError (child_process.js:613:13)
at Object.execSync (child_process.js:653:13)
at Object.childProcess.(anonymous function) [as execSync] (ELECTRON_ASAR.js:689:22)
at TaskWarriorExtension.onEnd (/Applications/Zendoro.app/Contents/Resources/app/main.js:155:15)
at extensions.forEach.e (/Applications/Zendoro.app/Contents/Resources/app/main.js:360:36)
at Array.forEach ()
at ZenFlow.transitionToIdle (/Applications/Zendoro.app/Contents/Resources/app/main.js:360:21)
at ZenFlow.cancelCurrentActivity (/Applications/Zendoro.app/Contents/Resources/app/main.js:332:12)
at click (/Applications/Zendoro.app/Contents/Resources/app/main.js:290:26)
at MenuItem.click (/Applications/Zendoro.app/Contents/Resources/electron.asar/browser/api/menu-item.js:55:9)

And after the timer completes by itself, it still throws:

Uncaught Exception:
Error: Command failed: /usr/local/bin/task stop 1
at checkExecSyncError (child_process.js:613:13)
at Object.execSync (child_process.js:653:13)
at Object.childProcess.(anonymous function) [as execSync] (ELECTRON_ASAR.js:689:22)
at TaskWarriorExtension.onEnd (/Applications/Zendoro.app/Contents/Resources/app/main.js:155:15)
at extensions.forEach.e (/Applications/Zendoro.app/Contents/Resources/app/main.js:360:36)
at Array.forEach ()
at ZenFlow.transitionToIdle (/Applications/Zendoro.app/Contents/Resources/app/main.js:360:21)
at ZenFlow.cancelCurrentActivity (/Applications/Zendoro.app/Contents/Resources/app/main.js:332:12)
at click (/Applications/Zendoro.app/Contents/Resources/app/main.js:290:26)
at MenuItem.click (/Applications/Zendoro.app/Contents/Resources/electron.asar/browser/api/menu-item.js:55:9)

To recover, I had to force quit the process and restart, which lead to resetting my #of completed pomodoros.