Remove the empty option from multiple-value select custom fields

For multiple-value selects, unlike vanilla version where we need to keep
the empty option so users can easily deselect all real values, current
selectpicker version doesn't need this workaround, just like the previous
chosen version.

share/html/Elements/EditCustomFieldSelect

@@ -175,7 +175,7 @@ my $use_chosen = CachedCustomFieldValues($CustomField)->Count >= 10 ? 1 : 0;
 $m->callback( CallbackName => 'Chosen', UseChosen => \$use_chosen, CustomField => $CustomField );
 
 # it's weird to see "(no value) X" in the input when selecting multiple values
-$show_empty_option = 0 if $use_chosen && $Multiple;
+$show_empty_option = 0 if $Multiple;
 </%init>
 <%ARGS>
 $Object => undef