Don't show a blue screen when the window is already closing

src/PowderToy.cpp

@@ -123,22 +123,30 @@ void BlueScreen(String detailMessage)
 	}
 }
 
+struct
+{
+	int sig;
+	const char *message;
+} signalMessages[] = {
+	{ SIGSEGV, "Memory read/write error" },
+	{ SIGFPE, "Floating point exception" },
+	{ SIGILL, "Program execution exception" },
+	{ SIGABRT, "Unexpected program abort" },
+	{ 0, nullptr },
+};
+
 void SigHandler(int signal)
 {
-	switch(signal){
+	const char *message = "Unknown signal";
-	case SIGSEGV:
+	for (auto *msg = signalMessages; msg->message; ++msg)
-		BlueScreen("Memory read/write error");
+	{
-		break;
+		if (msg->sig == signal)
-	case SIGFPE:
+		{
-		BlueScreen("Floating point exception");
+			message = msg->message;
-		break;
+			break;
-	case SIGILL:
+		}
-		BlueScreen("Program execution exception");
-		break;
-	case SIGABRT:
-		BlueScreen("Unexpected program abort");
-		break;
 	}
+	BlueScreen(ByteString(message).FromUtf8());
 }
 
 constexpr int SCALE_MAXIMUM = 10;
@@ -176,6 +184,11 @@ int main(int argc, char * argv[])
 {
 	Platform::SetupCrt();
 	Platform::Atexit([]() {
+		// Unregister dodgy error handlers so they don't try to show the blue screen when the window is closed
+		for (auto *msg = signalMessages; msg->message; ++msg)
+		{
+			signal(msg->sig, SIG_DFL);
+		}
 		SDLClose();
 		explicitSingletons.reset();
 	});
@@ -381,10 +394,10 @@ int main(int argc, char * argv[])
 	if (enableBluescreen)
 	{
 		//Get ready to catch any dodgy errors
-		signal(SIGSEGV, SigHandler);
+		for (auto *msg = signalMessages; msg->message; ++msg)
-		signal(SIGFPE, SigHandler);
+		{
-		signal(SIGILL, SigHandler);
+			signal(msg->sig, SigHandler);
-		signal(SIGABRT, SigHandler);
+		}
 	}
 
 	if constexpr (X86)