[shotwell/shotwell-0.30] publishing: Fix critical in Google Photos if target album is not set

[Jens Georg <jensgeorg src gnome org>]

commit f3f0e91eb0e310b6c0ffccb961ce4d5ee6074cb8
Author: Jens Georg <mail jensge org>
Date:   Thu May 7 08:40:48 2020 +0200

    publishing: Fix critical in Google Photos if target album is not set

 plugins/shotwell-publishing/PhotosPublisher.vala | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/plugins/shotwell-publishing/PhotosPublisher.vala 
b/plugins/shotwell-publishing/PhotosPublisher.vala
index ce5e5053..5f464700 100644
--- a/plugins/shotwell-publishing/PhotosPublisher.vala
+++ b/plugins/shotwell-publishing/PhotosPublisher.vala
@@ -47,7 +47,7 @@ internal class PublishingParameters {
         return target_album_name;
     }
 
-    public void set_target_album_name(string target_album_name) {
+    public void set_target_album_name(string? target_album_name) {
         this.target_album_name = target_album_name;
     }