fix: billable field behaviour for MOBILE_CAPTURE expenses (#3994)

Author: SahilK-027

src/app/fyle/add-edit-expense/add-edit-expense.page.ts

@@ -3668,8 +3668,21 @@ export class AddEditExpensePage implements OnInit {
     return null;
   }
 
-  getBillable(): boolean {
-    return this.getFormValues()?.billable;
+  /**
+   * If billable checkbox is visible (project selected + org has billable option),
+   *
+   * @returns the actual checkbox value (true/false),
+   *  otherwise return billableValue `undefined` because billable checkbox is hidden
+   */
+  getBillable(): boolean | undefined {
+    const formValues = this.getFormValues();
+    const billableValue = formValues?.billable;
+
+    if (formValues?.project && this.showBillable) {
+      return billableValue === true;
+    }
+
+    return billableValue;
   }
 
   getSkipRemibursement(): boolean {