Avoid duplicate sliders when switching between WEBP and JPEG (thanks adrianbjones for the report!); fix tabs

git-svn-id: http://svg-edit.googlecode.com/svn/trunk@2616 eee81c28-f429-11dd-99c0-75d572ba1ddd

editor/svg-editor.js

@@ -2575,8 +2575,10 @@
 				}, function () {
 					var sel = $(this);
 					if (sel.val() === 'JPEG' || sel.val() === 'WEBP') {
+						if (!$('#image-slider').length) {
 							$('<div><label>Quality: <input id="image-slider" type="range" min="1" max="100" value="92" /></label></div>').appendTo(sel.parent()); // Todo: i18n-ize label
 						}
+					}
 					else {
 						$('#image-slider').parent().remove();
 					}