[gnome-boxes] Report errors in Machine::get_screenshot_filename()

[Christophe Fergeau <teuf src gnome org>]

commit b04e43f298280e069900ec4478f18fc860ae41f0
Author: Christophe Fergeau <cfergeau redhat com>
Date:   Tue Sep 11 12:38:42 2012 +0200

    Report errors in Machine::get_screenshot_filename()
    
    When the VM has just been created, config.uuid is not known yet.
    When we quit Boxes from the wizard summary screen, the VM is deleted
    when it's in such a state, which causes Criticals on the console when
    it tries to delete the VM screenshot:
    
    (gnome-boxes:5027): Boxes-CRITICAL **: boxes_get_screenshot_filename:
    assertion `prefix != NULL' failed
    
    This commit changes get_screenshot_filename() to report errors by
    throwing a Boxes.Error exception and catches it in callers. This
    removes the get_screenshot_filename() criticals in the scenario
    described above.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=683792

 src/machine.vala |   11 +++++++++--
 1 files changed, 9 insertions(+), 2 deletions(-)
---
diff --git a/src/machine.vala b/src/machine.vala
index 871e66a..401b253 100644
--- a/src/machine.vala
+++ b/src/machine.vala
@@ -198,7 +198,10 @@ private abstract class Boxes.Machine: Boxes.CollectionItem, Boxes.IPropertiesPro
         }
     }
 
-    private string get_screenshot_filename () {
+    private string get_screenshot_filename () throws Boxes.Error {
+        if (config.uuid == null)
+            throw new Boxes.Error.INVALID ("no uuid, cannot build screenshot filename");
+
         return Boxes.get_screenshot_filename (config.uuid);
     }
 
@@ -430,7 +433,11 @@ private abstract class Boxes.Machine: Boxes.CollectionItem, Boxes.IPropertiesPro
         }
 
         config.delete ();
-        FileUtils.unlink (get_screenshot_filename ());
+        try {
+            FileUtils.unlink (get_screenshot_filename ());
+        } catch (Boxes.Error e) {
+            debug("Could not delete screenshot: %s", e.message);
+        }
     }
 
     public override void ui_state_changed () {