search-view: no show search view if field is empty

When the search field is empty is not needed show the result drop down.

https://bugzilla.gnome.org/show_bug.cgi?id=747962

data/ui/window.ui

@@ -291,7 +291,6 @@
     </child>
   </template>
   <object class="GcalSearchView" id="search_view">
-    <property name="visible" bind-source="search_bar" bind-property="search-mode-enabled" bind-flags="default | sync-create" />
     <property name="relative_to">search_entry</property>
     <property name="position">bottom</property>
     <signal name="event-activated" handler="search_event_selected" object="GcalWindow" swapped="no"/>