Missing library file handling is broken (another reason for "bpm detection never stops")

Symptom:
 - bpm detection never stops
 - song similarity detection never stops
 - the first time this happens the console claims that a mp3 or ogg file is missing then stops doing this
 - in the lower right corner of the banshee window a throbber turns indefinitely eating up about 12% of CPU power on a intel atom singlecore device

How to reproduce:
 - import new music to your library
 - use easytag, nautilus or the console to rename or delete the file before bpm detection and similarity detection for this file has finished. If you have a fast system it is perhaps best to deactivate these features first
 - enable the bpm detection and similarity detection again

Another way to trigger the problem:
 - Buy music from the ubuntuone music store
 - move it from "~/.ubuntuone/Purchased From Ubuntu One" to the music library

Activating the "re-scan music library" feature or plug-in or trying to trigger a music library re-scan manually doesn't fix the problem

Expected behavior:
 - If music is missing the respective files will be ignored but information about them is kept in the library: There is a chance that tey reside on an external memory that is currently not plugged in but that might return any moment. For details see the documentation of rhythmbox and shotwell that both work this way.

There is another bug report that nearly the same symptoms will be triggered by having non-audio files (e.G. text files) in the library but I expect it to really be a separate bug.

ProblemType: Bug
DistroRelease: Ubuntu 11.10
Package: banshee 2.2.0-1ubuntu2
ProcVersionSignature: Ubuntu 3.0.0-12.20-generic-pae 3.0.4
Uname: Linux 3.0.0-12-generic-pae i686
NonfreeKernelModules: nvidia wl
ApportVersion: 1.23-0ubuntu3
Architecture: i386
Date: Sun Oct 23 10:07:46 2011
EcryptfsInUse: Yes
ExecutablePath: /usr/lib/banshee/Banshee.exe
InterpreterPath: /usr/bin/mono
ProcEnviron:
 SHELL=/bin/bash
 PATH=(custom, user)
 LANG=en_US.UTF-8
 LC_TIME=de_DE.UTF-8
SourcePackage: banshee
UpgradeStatus: No upgrade log present (probably fresh install)