Pagecontainer: Remove a useless instruction.

Closes #8418
The `text` variable is first initialized to `this.placeholder`, which is
strictly equivalent to use `that.placeholder` inside the function used
just after. So in case `selected.length` is falsy, this is not necessary
to override `text` to the same value, i.e. its inital value.

Author: Hywan

js/widgets/forms/select.js

@@ -255,8 +255,6 @@ var selectmenu = $.widget( "mobile.selectmenu", [ {
 					text = selected.map( function() {
 						return $( this ).text();
 					} ).get().join( ", " );
-				} else {
-					text = that.placeholder;
 				}
 
 				if ( text ) {