web/elements: properly cleanup event handlers

Signed-off-by: Jens Langhammer <jens.langhammer@beryju.org>

web/src/elements/buttons/ModalButton.ts

@@ -64,14 +64,20 @@ export class ModalButton extends LitElement {
         ];
     }
 
-    constructor() {
+    firstUpdated(): void {
-        super();
+        window.addEventListener("keyup", this.keyUpHandler);
-        window.addEventListener("keyup", (e) => {
+    }
+
+    keyUpHandler = (e: KeyboardEvent) => {
         if (e.code === "Escape") {
             this.resetForms();
             this.open = false;
         }
-        });
+    }
+
+    disconnectedCallback(): void {
+        super.disconnectedCallback()
+        window.removeEventListener("keyup", this.keyUpHandler)
     }
 
     resetForms(): void {