Add a warning message when inserting a different type data

Steps to reproduce:
1. Create a new application using AWM.
2. When you define your structure, drag and drop the Number field
3. Save your application
4. Add an entry and insert first time only letters and after save the page. You will see that in View mode nothing is displayed.
5. Edit the entry and add numbers. The information is displayed correctly this time.
6. Edit the entry again and add letters and then save the page. This time in view mode you see the numbers introduced in the previous step.

It would be nice to have a warning message for when you try to insert another type data.