HistoryWindow: Center top widgets vertically

gajim/data/gui/history_window.ui

@@ -299,6 +299,7 @@
             <property name="visible">True</property>
             <property name="can_focus">False</property>
             <property name="halign">start</property>
+            <property name="valign">center</property>
             <property name="label" translatable="yes">Chat</property>
             <style>
               <class name="dim-label"/>
@@ -314,6 +315,7 @@
             <property name="visible">True</property>
             <property name="can_focus">True</property>
             <property name="tooltip_text" translatable="yes">Record history for this chat</property>
+            <property name="valign">center</property>
             <signal name="notify::active" handler="on_log_history_checkbutton_toggled" swapped="no"/>
           </object>
           <packing>
@@ -325,6 +327,7 @@
           <object class="GtkLabel">
             <property name="visible">True</property>
             <property name="can_focus">False</property>
+            <property name="valign">center</property>
             <property name="margin_left">6</property>
             <property name="label" translatable="yes">Record History</property>
             <style>
@@ -341,6 +344,7 @@
             <property name="width_request">400</property>
             <property name="visible">True</property>
             <property name="can_focus">False</property>
+            <property name="valign">center</property>
             <property name="hexpand">True</property>
             <property name="model">liststore1</property>
             <property name="tearoff_title" translatable="yes">Ttitle</property>