Add missing object check in mod manager (#731)

`HasMember` asserts `IsObject()` internally.
In release builds this is not an issue but this does not work on Debug builds.

Author: Jan200101

primedev/mods/modmanager.cpp

@@ -748,7 +748,7 @@ void ModManager::LoadMods()
 			continue;
 
 		// Add mod entry to enabledmods.json if it doesn't exist
-		if (!mod.m_bIsRemote && !m_EnabledModsCfg.HasMember(mod.Name.c_str()))
+		if (!mod.m_bIsRemote && m_bHasEnabledModsCfg && !m_EnabledModsCfg.HasMember(mod.Name.c_str()))
 		{
 			m_EnabledModsCfg.AddMember(rapidjson_document::StringRefType(mod.Name.c_str()), true, m_EnabledModsCfg.GetAllocator());
 			newModsDetected = true;