Don't print an error message for ERROR_PATH_NOT_FOUND in DirectoryIterator::Read

We do the same already for ERROR_FILE_NOT_FOUND. This fixes a harmless warning
when running the engine in a release directory where there is no planet/
directory.

src/platform/StdFile.cpp

@@ -975,6 +975,7 @@ void DirectoryIterator::Read(const char *dirname)
 	{
 		switch (GetLastError())
 		{
+		case ERROR_PATH_NOT_FOUND:
 		case ERROR_FILE_NOT_FOUND:
 			// This is okay, either the directory doesn't exist or there are no files
 			return;