fix: guard against courseGoals being undefined (#489)

No idea why this would happen honestly - it looks always defined
from the backend, and api.js doesn't transorm it. But we are seeing
JS errors related to it. So trying this as a first pass.

AA-848

src/course-home/outline-tab/OutlineTab.jsx

@@ -52,7 +52,7 @@ function OutlineTab({ intl }) {
     courseGoals: {
       goalOptions,
       selectedGoal,
-    },
+    } = {},
     datesBannerInfo,
     datesWidget: {
       courseDateBlocks,