Crash in recursive_insert

[romanbsd]

Unfortunately we weren't able to reproduce the crash locally, but it happens on arm devices in art.c:578 - add_child4(new_node, ref, l->key[depth+longest_prefix], SET_LEAF(l));

As far as I can tell, it's the access to l->key[depth+longest_prefix]

The assembly produced:

art.c:578
   633e6: 4435        add r5, r6
   633e8: 9803        ldr r0, [sp, #12]
   633ea: f044 0301   orr.w r3, r4, #1
   633ee: 4659        mov r1, fp
   633f0: 4428        add r0, r5
  *633f2: 7a02        ldrb  r2, [r0, #8]

I don't understand how it can happen, but it happens. Any ideas?