qt: avoid auto-updating window width when it's in full screen or when…

… it's maximized (#3771)

src/qt/bitcoingui.cpp

@@ -1180,6 +1180,9 @@ void BitcoinGUI::updateWidth()
  if (walletFrame == nullptr) {
  return;
  }
+ if (windowState() & (Qt::WindowMaximized | Qt::WindowFullScreen)) {
+ return;
+ }
  int nWidthWidestButton{0};
  int nButtonsVisible{0};
  for (QAbstractButton* button : tabGroup->buttons()) {