tdf#121904 use min size for attribute dialog

Change-Id: I98cdda7e384dce35f02d20d5b98b61168d34f786
Reviewed-on: https://gerrit.libreoffice.org/64554
Tested-by: Jenkins
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>

chart2/uiconfig/ui/attributedialog.ui

@@ -5,6 +5,8 @@
   <object class="GtkDialog" id="AttributeDialog">
     <property name="can_focus">False</property>
     <property name="border_width">6</property>
+    <property name="default_width">0</property>
+    <property name="default_height">0</property>
     <property name="type_hint">dialog</property>
     <child>
       <placeholder/>