Fix Ctrl-A then Ctrl-X infinite loop in quick_launch.

mash/quick_launch/quick_launch.cc

Index: mash/quick_launch/quick_launch.cc
diff --git a/mash/quick_launch/quick_launch.cc b/mash/quick_launch/quick_launch.cc
index dd5bc32a621eacf98acb68c9400ff4dd1e65a357..ceae8d7ad6d55da69b478fc17b5329e91f902dc0 100644
--- a/mash/quick_launch/quick_launch.cc
+++ b/mash/quick_launch/quick_launch.cc
@@ -96,6 +96,9 @@ class QuickLaunchUI : public views::WidgetDelegateView,
     if (suggestion_rejected_)
       return;
 
+    if (new_contents.empty())
+      return;
+
     // TODO(beng): it'd be nice if we persisted some history/scoring here.
     for (const auto& name : app_names_) {
       if (base::StartsWith(name, new_contents,