I was having the same problem when I started adding Aviary into the project I´m working on.
Finally I´ve managed to solve it by changing the style adding an extra line due to I didn´t wanted to change any line code from Aviary:
<style name="Theme.Base.AppCompat.Dialog.FixedSize" parent="Base.Theme.AppCompat.Dialog.FixedSize">
</style>
it seems that Base has been add so it changes completely the style name.
Before was Theme.Base.AppCompat.Dialog.FixedSize and now is Base.Theme.AppCompat.Dialog.FixedSize
btw, I´ve also changed my theme to:
<style name="AppTheme" parent="Base.Theme.AppCompat.Light.DarkActionBar">
<!-- Customize your theme here. -->
</style>
I hope this help you to solve the problem.