GetFeeds must always discard actions with dangling repo_id (#19598)

* GetFeeds must always discard actions with dangling repo_id

See https://discourse.gitea.io/t/blank-page-after-login/5051/12
for a panic in 1.16.6.

* add comment to explain the dangling ID in the fixture

* loadRepoOwner must not attempt to use a nil action.Repo

* make fmt

Co-authored-by: Loïc Dachary <loic@dachary.org>

models/action_test.go

@@ -211,3 +211,20 @@ func TestNotifyWatchers(t *testing.T) {
 		OpType:    action.OpType,
 	})
 }
+
+func TestGetFeedsCorrupted(t *testing.T) {
+	assert.NoError(t, unittest.PrepareTestDatabase())
+	user := unittest.AssertExistsAndLoadBean(t, &user_model.User{ID: 1}).(*user_model.User)
+	unittest.AssertExistsAndLoadBean(t, &Action{
+		ID:     8,
+		RepoID: 1700,
+	})
+
+	actions, err := GetFeeds(db.DefaultContext, GetFeedsOptions{
+		RequestedUser:  user,
+		Actor:          user,
+		IncludePrivate: true,
+	})
+	assert.NoError(t, err)
+	assert.Len(t, actions, 0)
+}