[core/hle/services/am] Fix MK8D crash (#4313)

Signed-off-by: lizzie <lizzie@eden-emu.dev>

- [x] I have read and followed the [Contribution Guidelines](https://git.eden-emu.dev/eden-emu/eden/src/branch/master/CONTRIBUTING.md#code-contributions).
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- [x] I have read and followed the [Coding Guidelines](https://git.eden-emu.dev/eden-emu/eden/src/branch/master/docs/policies/Coding.md) to the best of my ability.

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This fixes a random mk8d crash when connecting via LDN

Reviewed-on: https://git.eden-emu.dev/eden-emu/eden/pulls/4313
Reviewed-by: CamilleLaVey <camillelavey99@gmail.com>
Reviewed-by: MaranBr <maranbr@eden-emu.dev>

src/core/hle/service/am/service/application_functions.cpp

@@ -324,6 +324,7 @@ Result IApplicationFunctions::NotifyRunning(Out<bool> out_became_running) {
 
 Result IApplicationFunctions::GetPseudoDeviceId(Out<Common::UUID> out_pseudo_device_id) {
     LOG_WARNING(Service_AM, "(stubbed)");
+    R_UNLESS(out_pseudo_device_id, ResultUnknown);
 
     // This should be hashed with the device specific hash
     // for now this will do