fix(select): return undefined when there are no options (#11968)

* fix(select): make select with no options return undefined when OK is pressed (#10435)

* refactor(select): add early check for alert inputs

fixes #10435

src/components/alert/alert-component.ts

@@ -316,6 +316,11 @@ export class AlertCmp {
       return this.d.inputs.filter(i => i.checked).map(i => i.value);
     }
 
+    if (this.d.inputs.length === 0) {
+      // this is an alert without any options/inputs at all
+      return undefined;
+    }
+
     // this is an alert with text inputs
     // return an object of all the values with the input name as the key
     const values: {[k: string]: string} = {};