This crash was happening with Kdenlive 0.9.10, so I compiled the latest from source code but still the same problem.

For me it happens all the time when the Region transition is between two video clips. I tested it with two color clips but it didn't crash, tested it again with other video clips and it crashed.

Tested with Kdenlive 0.9.10 from rpmfusion for Fedora 22 / KDE 15.3.0
Tested again with Kdenlive from git + mlt 0.9.8 compiled against Qt 5.5.0

Reproducible: Always

Steps to Reproduce:
1. Place two video clips in different tracks (e.g Track1 and Track2) 
2. Add a Region transition between the two tracks
3. Change the "Alpha Channel Operation" of the Region transition from "Over" to "And", "Or" or "Xor"

Actual Results:  
The program crashed immediately or when trying to play the area with the transition

Expected Results:  
Not crash

Here is the crash info from gdb:

Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x7fffaec15700 (LWP 5835)]
composite_line_yuv_xor (
    dest=0x7fff56375cb0 "@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200"..., 
    src=0x7fff5687a610 "@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200@\200"..., width=1920, 
    alpha_b=0x1 <error: Cannot access memory at address 0x1>, alpha_a=0x0, weight=65536, luma=0x7fff98c4f980, soft=0, step=65535)
    at transition_composite.c:430
430                     mix = calculate_mix( luma, j, soft, weight, *alpha_b ++ ^ *alpha_a, step );