[geary] Fix some compile warnings

[Michael Gratton <mjog src gnome org>]

commit e6200125f8bdf546d6a1cb9250011f658924cd22
Author: Michael Gratton <mike vee net>
Date:   Mon Feb 18 12:06:06 2019 +1100

    Fix some compile warnings

 src/client/application/geary-controller.vala | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/src/client/application/geary-controller.vala b/src/client/application/geary-controller.vala
index 42995f93..f94b8fb4 100644
--- a/src/client/application/geary-controller.vala
+++ b/src/client/application/geary-controller.vala
@@ -753,8 +753,8 @@ public class GearyController : Geary.BaseObject {
         } else if (this.account_manager.is_goa_account(account)) {
             context.authentication_prompting = true;
             try {
-                account.load_incoming_credentials(context.cancellable);
-                account.load_outgoing_credentials(context.cancellable);
+                yield account.load_incoming_credentials(context.cancellable);
+                yield account.load_outgoing_credentials(context.cancellable);
             } catch (GLib.Error err) {
                 // Bail out right away, but probably should be opening
                 // the GOA control panel.