Handle key credential manager (Windows Hello) failure

The KeyCredentialManager::RequestCreateAsync call can fail because we
can end up in a situation where Windows Hello is initially available but
then becomes unavailable, such as during a remote desktop session. This
commit prevents a crash by moving the call into the try-catch.

Fixes keepassxreboot#7890, but does not improve the experience yet.

src/winhello/WindowsHello.cpp

@@ -64,19 +64,18 @@ namespace
             array_view<uint8_t>(reinterpret_cast<uint8_t*>(challenge.data()), challenge.size()));
 
         return AsyncTask::runAndWaitForFuture([&] {
-            // The first time this is used a key-pair will be generated using the common name
-            auto result =
-                KeyCredentialManager::RequestCreateAsync(s_winHelloKeyName, KeyCredentialCreationOption::FailIfExists)
-                    .get();
-
-            if (result.Status() == KeyCredentialStatus::CredentialAlreadyExists) {
-                result = KeyCredentialManager::OpenAsync(s_winHelloKeyName).get();
-            } else if (result.Status() != KeyCredentialStatus::Success) {
-                error = QObject::tr("Failed to create Windows Hello credential.");
-                return false;
-            }
-
             try {
+				// The first time this is used a key-pair will be generated using the common name
+				auto result =
+                KeyCredentialManager::RequestCreateAsync(s_winHelloKeyName, KeyCredentialCreationOption::FailIfExists)
+						.get();
+
+				if (result.Status() == KeyCredentialStatus::CredentialAlreadyExists) {
+					result = KeyCredentialManager::OpenAsync(s_winHelloKeyName).get();
+				} else if (result.Status() != KeyCredentialStatus::Success) {
+					error = QObject::tr("Failed to create Windows Hello credential.");
+					return false;
+				}
                 const auto signature = result.Credential().RequestSignAsync(challengeBuffer).get();
                 if (signature.Status() != KeyCredentialStatus::Success) {
                     error = QObject::tr("Failed to sign challenge using Windows Hello.");