exposure optimiser incorrectly ignoring some pairs

[Pwomack]

I noticed on a large pano that some images had not been exposure optimised.
IN an attempt to force the issue, I reduced the pano to two images, a reference
and the unoptimised "fault".

On repeating the exposure optimise command, I was told the images
had no overlapping pixels, which may well explain the lack of optimisation
in the larger pano, but it happens to be false!

"Error: no overlapping points found, Photometric optimisation aborted"

I have attached the test case; to make the images smaller I edited
them to be a flat colour, which compresses very well :-)

[Pwomack (pwomack)]

I'm guessing some version information is wanted; here's the "system" tab from the "about" menu

Operating System: Linux 3.13.0-63-generic x86_64
Architecture: 64 bit
Free memory: 6702668 kiB

Hugin
Version: 2015.0.0.cdefc6e53a58
Path to resources: /usr/share/hugin/xrc/
Path to data: /usr/share/hugin/data/
Hugins camera and lens database: /home/bugbear/.hugindata/camlens.db
Multi-threading using C++11 std::thread and OpenMP

Libraries
wxWidgets: wxWidgets 3.0
wxWidgets Library (wxGTK port)
Version 3.0.0 (Unicode: wchar_t, debug level: 1),
compiled at Dec 2 2013 15:56:33

Runtime version of toolkit used is 2.24.
Compile-time GTK+ version is 2.24.22.

libpano13: 2.9.19
Boost: 1.54.0
Exiv2: 0.23
SQLite3: 3.8.2
Vigra: 1.10.0

[tmodes (tmodes)]

Fixed in changeset f2e38d537544