fix: Connections can be highlighted multiple times (#6502)

* fix: Connections can be highlighted multiple times

* fix: remove spaces to fix clang-formating

core/rendered_connection.ts

@@ -280,6 +280,10 @@ export class RenderedConnection extends Connection {
 
   /** Add highlighting around this connection. */
   highlight() {
+    if (this.highlightPath) {
+      // This connection is already highlighted
+      return;
+    }
     let steps;
     const sourceBlockSvg = (this.sourceBlock_);
     const renderConstants =