windows/serialInterface: Chopped off an extra nul that was getting pu…

…t on the end of the read registry string key

src/windows/serialInterface.cxx

@@ -94,6 +94,7 @@ struct hklmRegistryKey_t
 			displayError(result, "retrieve value for key"sv, keyName);
 			return {};
 		}
+		value.resize(value.length() - 1U);
 		return value;
 	}
 };