[REG 5.3-5.4] Android: QFileDialog for Save Keeps Save Button Disabled until the filename contains a dot

To reproduce:

1. Build textedit example against 5.4.0;
2. Run the example on a device;
3. Write/chage some text in the QTextEdit window;
4. Tap on button Save;
5. Observe that appears QFileDialog;
6. Select a writable folder;
7. Try to write some file name using letters only:
i.e.: myfile
8. Observe that the Save button is still disabled
9. After the filename, place some non-alphanumeric character:
perion, comma, space etc. and observe that Save button comes
to be enabled and now you can save your file

10. Build the example versus 5.4.0 for Linux and run it
on linux.
Proceed with the steps 3 to 7 and observe
that the issue is not existing and you can save your file
as "myfile" without any need to place additional
non-alphanumeric character.

Therefore, I beleive that the issue is Android-specific.