boxcat: Silence an unused variable warning

On parse errors, we can log out the explanatory string indicating what
the parsing error was, rather than just ignoring the variable and
returning an overly broad error code.

src/core/hle/service/bcat/backend/boxcat.cpp

@@ -495,7 +495,8 @@ Boxcat::StatusResult Boxcat::GetStatus(std::optional<std::string>& global,
         }
 
         return StatusResult::Success;
-    } catch (const nlohmann::json::parse_error& e) {
+    } catch (const nlohmann::json::parse_error& error) {
+        LOG_ERROR(Service_BCAT, "{}", error.what());
         return StatusResult::ParseError;
     }
 }