fix tag values with whitespace causing css bugs (#9637)

modules/svg/tag_classes.js

@@ -159,7 +159,12 @@ export function svgTagClasses() {
             classes.push('tag-wikidata');
         }
 
-        return classes.join(' ').trim();
+        // ensure that classes for tags keys/values with special characters like spaces
+        // are not added to the DOM, because it can cause bizarre issues (#9448)
+        return classes
+            .filter(klass => /^[-_a-z0-9]+$/.test(klass))
+            .join(' ')
+            .trim();
     };