fix(drp): guard visible months for invalid values

Author: ddaribo

src/components/date-range-picker/date-range-picker.common.spec.ts

@@ -87,6 +87,15 @@ describe('Date range picker - common tests for single and two inputs mode', () =
       picker.visibleMonths = 11;
       await elementUpdated(picker);
       expect(picker.visibleMonths).to.equal(2);
+
+      // test with NaN or undefined
+      picker.visibleMonths = Number.NaN;
+      await elementUpdated(picker);
+      expect(picker.visibleMonths).to.equal(2);
+
+      picker.visibleMonths = undefined as any;
+      await elementUpdated(picker);
+      expect(picker.visibleMonths).to.equal(2);
     });
 
     it('should set the visibleMonths property via attribute', async () => {

src/components/date-range-picker/date-range-picker.ts

@@ -49,6 +49,7 @@ import {
   defaultDateRangeTransformers,
 } from '../common/mixins/forms/form-value.js';
 import {
+  asNumber,
   clamp,
   createCounter,
   equal,
@@ -515,7 +516,7 @@ export default class IgcDateRangePickerComponent extends FormAssociatedRequiredM
   }
 
   public set visibleMonths(value: number) {
-    this._visibleMonths = clamp(value, 1, 2);
+    this._visibleMonths = clamp(asNumber(value, 2), 1, 2);
   }
   /**
    * The orientation of the calendar header.