Fixed|libdeng2|ArchiveFeed: Handling corrupt source data

Even if the source archive was invalid and caused an exception when
reading, the feed was still added to the source file's deletion
audience. However, the exception caused the ArchiveFeed constructor
to be automatically undone, leaving an invalid pointer in the source
file's audience.

doomsday/libdeng2/src/filesys/archivefeed.cpp

@@ -48,8 +48,6 @@ DENG2_PIMPL(ArchiveFeed)
 
     Instance(Public *feed, File &f) : Base(feed), file(&f), arch(0), parentFeed(0)
     {
-        file->audienceForDeletion() += this;
-
         // If the file happens to be a byte array file, we can use it
         // directly to store the Archive.
         if(IByteArray *bytes = f.maybeAs<IByteArray>())
@@ -67,6 +65,8 @@ DENG2_PIMPL(ArchiveFeed)
             f >> serializedArchive;
             arch = new ZipArchive(serializedArchive);
         }
+
+        file->audienceForDeletion() += this;
     }
 
     Instance(Public *feed, ArchiveFeed &parentFeed, String const &path)