Fix couple of crashes in secondary windows.

Telegram/SourceFiles/boxes/peers/edit_peer_info_box.cpp

@@ -2200,8 +2200,11 @@ void Controller::saveForum() {
 		channel->inputChannel,
 		MTP_bool(*_savingData.forum)
 	)).done([=](const MTPUpdates &result) {
+		const auto weak = base::make_weak(this);
 		channel->session().api().applyUpdates(result);
-		continueSave();
+		if (weak) { // todo better to be able to save in closed already box.
+			continueSave();
+		}
 	}).fail([=](const MTP::Error &error) {
 		if (error.type() == u"CHAT_NOT_MODIFIED"_q) {
 			continueSave();

Telegram/SourceFiles/mainwidget.cpp

@@ -1192,9 +1192,11 @@ void MainWidget::setInnerFocus() {
 			_mainSection->setInnerFocus();
 		} else if (!_hider && _thirdSection) {
 			_thirdSection->setInnerFocus();
-		} else {
-			Assert(_dialogs != nullptr);
+		} else if (_dialogs) {
 			_dialogs->setInnerFocus();
+		} else {
+			// Maybe we're just closing a child window, content is destroyed.
+			_history->setFocus();
 		}
 	} else if (_mainSection) {
 		_mainSection->setInnerFocus();
@@ -1293,8 +1295,9 @@ void MainWidget::showHistory(
 		}
 		const auto unavailable = peer->computeUnavailableReason();
 		if (!unavailable.isEmpty()) {
-			Assert(isPrimary()); // windows todo
-			if (params.activation != anim::activation::background) {
+			if (!isPrimary()) {
+				_controller->window().close();
+			} else if (params.activation != anim::activation::background) {
 				_controller->show(Ui::MakeInformBox(unavailable));
 				_controller->window().activate();
 			}
@@ -1950,10 +1953,9 @@ void MainWidget::showNonPremiumLimitToast(bool download) {
 	});
 }
 
-void MainWidget::showBackFromStack(
-		const SectionShow &params) {
+bool MainWidget::showBackFromStack(const SectionShow &params) {
 	if (preventsCloseSection([=] { showBackFromStack(params); }, params)) {
-		return;
+		return false;
 	}
 
 	if (_stack.empty()) {
@@ -1963,7 +1965,7 @@ void MainWidget::showBackFromStack(
 		crl::on_main(this, [=] {
 			_controller->widget()->setInnerFocus();
 		});
-		return;
+		return (_dialogs != nullptr);
 	}
 	auto item = std::move(_stack.back());
 	_stack.pop_back();
@@ -1995,6 +1997,7 @@ void MainWidget::showBackFromStack(
 				anim::activation::background));
 
 	}
+	return true;
 }
 
 void MainWidget::orderWidgets() {

Telegram/SourceFiles/mainwidget.h

@@ -152,8 +152,7 @@ public:
 		const SectionShow &params);
 	void updateColumnLayout();
 	bool stackIsEmpty() const;
-	void showBackFromStack(
-		const SectionShow &params);
+	bool showBackFromStack(const SectionShow &params);
 	void orderWidgets();
 	QPixmap grabForShowAnimation(const Window::SectionSlideParams &params);
 	void checkMainSectionToLayer();

Telegram/SourceFiles/window/window_session_controller.cpp

@@ -1660,8 +1660,9 @@ void SessionController::showForum(
 	) | rpl::start_with_next([=, history = forum->history()] {
 		const auto now = activeChatCurrent().owningHistory();
 		const auto showHistory = !now || (now == history);
+		const auto weak = base::make_weak(this);
 		closeForum();
-		if (showHistory) {
+		if (weak && showHistory) {
 			showPeerHistory(history, {
 				SectionShow::Way::Backward,
 				anim::type::normal,
@@ -1676,7 +1677,7 @@ void SessionController::closeForum() {
 	if (const auto forum = _shownForum.current()) {
 		const auto id = windowId();
 		if (id.type == SeparateType::Forum) {
-			const auto initial = id.thread->asForum();
+			const auto initial = id.forum();
 			if (!initial || initial == forum) {
 				Core::App().closeWindow(_window);
 			} else {
@@ -2529,7 +2530,13 @@ void SessionController::showBackFromStack(const SectionShow &params) {
 		return topic && topic->forum()->topicDeleted(topic->rootId());
 	};
 	do {
-		content()->showBackFromStack(params);
+		const auto empty = content()->stackIsEmpty();
+		const auto shown = content()->showBackFromStack(params);
+		if (empty && !shown && content()->stackIsEmpty() && bad()) {
+			clearSectionStack(anim::type::instant);
+			window().close();
+			break;
+		}
 	} while (bad());
 }