[win32] RP_ExtractImage: Fix an issue with directory thumbnailing for…

… unsupported directories.

RP_ExtractImage::Load() needs to return E_FAIL, not S_OK, if the directory
is unsupported. Otherwise, Windows will show a regular directory icon,
without thumbnailing the directory's contents.

Fixes #427: No Thumbnails after install
Reported by @Conan179.

NEWS.md

@@ -1,5 +1,13 @@
 # Changes
 
+## v2.4.1 (released 2024/11/12)
+
+* Bug fixes:
+  * Windows: Fix an issue with directory thumbnailing that broke Windows'
+    built-in directory thumbnailer if the directory isn't supported.
+    * Fixes #427: No Thumbnails after install
+      * Reported by @Conan179.
+
 ## v2.4 (released 2024/11/10)
 
 * New features:

src/win32/RP_ExtractImage.cpp

@@ -121,16 +121,22 @@ IFACEMETHODIMP RP_ExtractImage::Load(_In_ LPCOLESTR pszFileName, DWORD dwMode)
 	}
 
 	// If ThumbnailDirectoryPackages is disabled, make sure this is *not* a directory.
+	const bool is_directory = FileSystem::is_directory(d->olefilename);
 	if (!config->getBoolConfigOption(Config::BoolConfig::Options_ThumbnailDirectoryPackages)) {
-		if (FileSystem::is_directory(d->olefilename)) {
+		if (is_directory) {
 			// It's a directory. Don't thumbnail it.
-			return S_OK;
+			return E_FAIL;
 		}
 	}
 
 	// Get the appropriate RomData class for this ROM.
 	// RomData class *must* support at least one image type.
 	d->romData = RomDataFactory::create(d->olefilename, RomDataFactory::RDA_HAS_THUMBNAIL);
+	if (!d->romData && is_directory) {
+		// Unable to thumbnail this RomData class, and it's a directory.
+		// Return E_FAIL in order to allow Explorer to thumbnail the directory normally.
+		return E_FAIL;
+	}
 	return S_OK;
 }