applets/swkbd: Only read the text check message on Failure/Confirm

Applications may leave this region of memory uninitialized when the text check result is not either Failure or Confirm.
Attempting to read uninitialized memory may cause an exception within the UTF16 to UTF8 string converter.
Fix this by only reading the text check message on Failure or Confirm.

src/core/hle/service/am/applets/software_keyboard.cpp

@@ -273,8 +273,13 @@ void SoftwareKeyboard::ProcessTextCheck() {
 
     std::memcpy(&swkbd_text_check, text_check_data.data(), sizeof(SwkbdTextCheck));
 
-    std::u16string text_check_message = Common::UTF16StringFromFixedZeroTerminatedBuffer(
-        swkbd_text_check.text_check_message.data(), swkbd_text_check.text_check_message.size());
+    std::u16string text_check_message =
+        swkbd_text_check.text_check_result == SwkbdTextCheckResult::Failure ||
+                swkbd_text_check.text_check_result == SwkbdTextCheckResult::Confirm
+            ? Common::UTF16StringFromFixedZeroTerminatedBuffer(
+                  swkbd_text_check.text_check_message.data(),
+                  swkbd_text_check.text_check_message.size())
+            : u"";
 
     LOG_INFO(Service_AM, "\nTextCheckResult: {}\nTextCheckMessage: {}",
              GetTextCheckResultName(swkbd_text_check.text_check_result),