fix attribute errors in @lazyproperty methods

Allura/allura/model/project.py

@@ -463,6 +463,8 @@ def icon_max_size(self):
 
     @LazyProperty
     def icon_timestamp(self):
+        if not self.icon:
+            return None
         return timegm(self.icon._id.generation_time.timetuple())
 
     @property

Allura/allura/model/repository.py

@@ -861,12 +861,12 @@ def creator_url(self):
     @LazyProperty
     def downstream_url(self):
         with self.push_downstream_context():
-            return c.app.url
+            return c.app.url if c.app else None
 
     @LazyProperty
     def downstream_repo(self):
         with self.push_downstream_context():
-            return c.app.repo
+            return c.app.repo if c.app else None
 
     def push_downstream_context(self):
         return h.push_context(self.downstream.project_id, self.downstream.mount_point)
@@ -1610,6 +1610,15 @@ def size(self):
     def __bool__(self):
         return False
 
+    def content_type(self):
+        return None
+
+    def content_encoding(self):
+        return None
+
+    def has_html_view(self):
+        return False
+
 
 class Symlink(Blob):
     # maybe this shouldn't inherit from Blob, but its handy for now and works well with git (where symlinks are blobs)