fix icons background

src/assets/styles/_buttons.scss

@@ -67,6 +67,10 @@ iqser-circle-button {
             background: rgba($primary, 0.1);
         }
 
+        &:not(.overlay):hover {
+            background-color: $btn-bg;
+        }
+
         &.primary {
             font-weight: 500 !important;
             background-color: $primary;

src/lib/filtering/models/filter-group.model.ts

@@ -8,8 +8,7 @@ export interface FilterGroup {
     readonly icon?: string;
     readonly filterTemplate?: TemplateRef<any>;
     readonly hide?: boolean;
-    readonly checker: Function;
+    readonly checker?: Function;
     readonly matchAll?: boolean;
     readonly checkerArgs?: any[];
-
 }