[CODE] Fix forward declaration edge case

Source/FixItCore/Private/FixItCore.cpp

@@ -23,6 +23,11 @@ namespace {
 	}
 }
 
+// Implementations, even if defaulted, must be in the implementation file
+// (for forward declarations and TUniquePtr usage)
+FFixItCoreModule::FFixItCoreModule() = default;
+FFixItCoreModule::~FFixItCoreModule() = default;
+
 void FFixItCoreModule::StartupModule()
 {
 #if PLATFORM_WINDOWS

Source/FixItCore/Public/FixItCore.h

@@ -20,8 +20,8 @@ class FIXITCORE_API FFixItCoreModule : public IModuleInterface
 {
 public:
 	// Those need to be defined due to a field TUniquePtr<FForwarDeclaredStruct>
-	//FFixItCoreModule();
-	//~FFixItCoreModule();
+	FFixItCoreModule();
+	~FFixItCoreModule();
 
 	// Begin IModuleInterface interface
 	virtual void StartupModule() override;