luci-base: don't treat .rmempty flag as optional for ListValue widgets

Restore the old CBI behaviour of not automatically rendering empty
selection choices in ListValue select dropdowns when .rmempty is
specified.

Signed-off-by: Jo-Philipp Wich <jo@mein.io>

modules/luci-base/htdocs/luci-static/resources/form.js

@@ -1460,7 +1460,7 @@ var CBIListValue = CBIValue.extend({
 			id: this.cbid(section_id),
 			size: this.size,
 			sort: this.keylist,
-			optional: this.rmempty || this.optional,
+			optional: this.optional,
 			placeholder: this.placeholder,
 			validate: L.bind(this.validate, this, section_id)
 		});

modules/luci-base/htdocs/luci-static/resources/ui.js

@@ -243,7 +243,7 @@ var UISelect = UIElement.extend({
 				'multiple': this.options.multiple ? '' : null
 			}));
 
-			if (this.options.optional)
+			if (this.options.optional || this.choices.hasOwnProperty(''))
 				frameEl.lastChild.appendChild(E('option', {
 					'value': '',
 					'selected': (this.values.length == 0 || this.values[0] == '') ? '' : null

modules/luci-base/luasrc/view/cbi/lvalue.htm

@@ -7,7 +7,7 @@
 		sort = self.keylist,
 		widget = self.widget,
 		datatype = self.datatype,
-		optional = self.optional or self.rmempty,
+		optional = self.optional,
 		placeholder = self.placeholder
 	}
 }))%>></div>