bcat/backend: Prevent fmt exception in debug log within NullBackend::Clear()

A formatting specifier within Clear wasn't being used, which will cause
fmt to throw an exception. This fixes that.

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

@@ -117,7 +117,7 @@ bool NullBackend::SynchronizeDirectory(TitleIDVersion title, std::string name,
 }
 
 bool NullBackend::Clear(u64 title_id) {
-    LOG_DEBUG(Service_BCAT, "called, title_id={:016X}");
+    LOG_DEBUG(Service_BCAT, "called, title_id={:016X}", title_id);
 
     return true;
 }