Bitcoin-qt -testnet 0.17.1 Send and Receive buttons do nothing Fully synced on testnet blockchain after building Bitcoin with UI and wallet enabled on Ubuntu 18.10.

Pressing Send and Receive buttons results in no UI displayed.

Receiving addresses dialog doesn't have New button in this version so it can't be used.

Debug window getnewaddress worked, however, and I was able to receive some coins from coinfaucet.eu using that address.

After receiving coins Send button still doesn't result in any UI displayed.
Receiving addresses menu/resulting dialog now shows the address that coins were received at (the one obtained via getnewaddress).

I see the same behavior of buttons when synced on the main net but couldn't test sending or receiving the real Bitcoins.

What can I do to debug this issue without getting deep into the (quite unfamiliar at this point) source code? I compiled bitcoin with optimizations enabled.

Here is a link to the debug.log created in the following way: exited bitcoin-qt and renamed original log which was huge. Restarted bitcoin-qt with options -testnet -debug=1. Clicked on Send, Receive and Transactions buttons. Exited bitcoin-qt.
I believe I should answer this question for the people who may stumble here and would like to know right away what is this issue all about.

If you are building from source and configure your build like:

./configure --with-gui --disable-wallet --SOME-OTHER-OPTIONS

and then you decide you want the wallet and go back to configure and rebuild without --disable-wallet, that is:

./configure --with-gui --SOME-OTHER-OPTIONS

make sure you run make clean before rebuilding.