qt: Make sure splash screen is freed on AppInitMain fail

The `splashFinished` event was never sent if AppInitMain fails,
causing the splash screen to stick around, causing problems
later.

This bug has existed for a while but is now trigging potential crashed
because the splash screen subscribes to wallet events.

Meant to fix #12372.

Signed-off-by: Wladimir J. van der Laan <laanwj@gmail.com>

src/qt/bitcoin.cpp

@@ -516,6 +516,7 @@ void BitcoinApplication::initializeResult(bool success)
         QTimer::singleShot(100, paymentServer, SLOT(uiReady()));
 #endif
     } else {
+        Q_EMIT splashFinished(window);
         quit(); // Exit main loop
     }
 }