[ptx] hugin crashes when removing images

[Rich]

try removing selection of images containing more than one image, 
starting from down.

(for example, add 3 images and select 2nd & 3rd image; remove them)

->
hugin: Panorama.cpp:326: const PT::VariableMap& 
PT::Panorama::getImageVariables(unsigned int) const: Assertion `imgNr < 
state
.images.size()' failed.
Aborted

hugin cvs050602
-- 
  Rich