do not download svg images on windows

gtk-message.go

@@ -14,6 +14,7 @@ import (
 	"mellium.im/xmpp/jid"
 	"os"
 	"path/filepath"
+	"runtime"
 )
 
 func generatePresenceWidget(p stanza.Packet) gtk.Widgetter {
@@ -206,7 +207,7 @@ func getAvatar(j, hash string) *gtk.Image { // TODO: This function probably shou
 	}
 
 	base64_data := card.Photo.Binval
-	if card.Photo.Binval == "" {
+	if card.Photo.Binval == "" || (card.Photo.Type == "image/svg+xml" && runtime.GOOS == "windows") {
 		return newImageFromPath("debug.png")
 	}