Comment 2 for bug 1239514

StacktraceTop:
 __libc_message (do_abort=2, fmt=0x7ffd5a128240 "ned long)(((mchunkptr)((char*)(victim) - 2*(sizeof(size_t))))) & ~((2 * (4 * 1024 * 1024 * sizeof(long)))-1)))->ar_ptr : &main_arena)") at ../sysdeps/unix/sysv/linux/libc_fatal.c:171
 heap_trim (pad=140726119509441, heap=0x6e7) at arena.c:677
 _int_free (av=0x6a, p=<optimized out>, have_lock=0) at malloc.c:3987
 initialize_backend (cbdav=cbdav@entry=0x375a1e0, perror=perror@entry=0x7ffd425a3ca8) at e-cal-backend-caldav.c:2854
 caldav_do_open (backend=0x375a1e0, cal=<optimized out>, cancellable=0x386ca80, only_if_exists=<optimized out>, perror=0x7ffd425a3ca8) at e-cal-backend-caldav.c:2948