Display fallback icon iin the effects tab if no icon is available

src/module/active-effect.ts

@@ -13,6 +13,11 @@ declare global {
 
 type PromisedType<T> = T extends Promise<infer U> ? U : T;
 export class DS4ActiveEffect extends ActiveEffect {
+    /**
+     * A fallback icon that can be used if no icon is defined for the effect.
+     */
+    static FALLBACK_ICON = "icons/svg/aura.svg";
+
     /**
      * A cached reference to the source document to avoid recurring database lookups
      */