EXT-6542 Localized the "none/none" in the About land floater.

This is an additional fix to the one made in rev. 6788ff579917.

Reviewed by Mike Antipov at https://codereview.productengine.com/secondlife/r/828/

--HG--
branch : product-engine

indra/newview/llpanellandmedia.cpp

@@ -151,7 +151,7 @@ void LLPanelLandMedia::refresh()
 		mMediaDescEdit->setEnabled( can_change_media );
 
 		std::string mime_type = parcel->getMediaType();
-		if (mime_type.empty())
+		if (mime_type.empty() || mime_type == LLMIMETypes::getDefaultMimeType())
 		{
 			mime_type = LLMIMETypes::getDefaultMimeTypeTranslation();
 		}