Bugfixes: don't select dirs and don't crash on write settings

Only select files when archiving pics from filemanager. While at it, I
noticed a crash on close when no item is selected in PicturesWidget. So
check if MappingData is valid on writing settings. Best way is
MappingData::isValid(), and for that I needed a explicit constructor.

1 files changed, 2 insertions, 0 deletions

diff --git a/mappingtreemodel.h b/mappingtreemodel.h
index a4a1ae8..fa91a78 100644
--- a/mappingtreemodel.h
+++ b/mappingtreemodel.h
@@ -117,6 +117,8 @@ class MappingTreeResultModel : public SmTreeModel {
 };
 
 struct MappingData {
+    MappingData();
+    bool isValid();
     int mappingId;
     int parentId;
     int myId;