Fix UAF in comps_objmrtree_unite function

The added field is not used at all in many places and it is probably the
left-over of some copy-paste.
COMPS_HSList ** comps_mrtree_getp(COMPS_MRTree * rt, const char * key) {
    COMPS_HSList * subnodes;
    COMPS_HSListItem * it = NULL;
    COMPS_MRTreeData * rtdata;
    unsigned int offset, len, x;
    char found, ended;

    len = strlen(key);
    offset = 0;
    subnodes = rt->subnodes;
    while (offset != len) {
        found = 0;
        for (it = subnodes->first; it != NULL; it=it->next) {
            if (((COMPS_MRTreeData*)it->data)->key[0] == key[offset]) {
                found = 1;
                break;
            }
        }
        if (!found)
            return NULL;
        rtdata = (COMPS_MRTreeData*)it->data;

        for (x=1; ;x++) {
            ended=0;
            if (rtdata->key[x] == 0) ended += 1;
            if (x == len - offset) ended += 2;
            if (ended != 0) break;
            if (key[offset+x] != rtdata->key[x]) break;
        }
        if (ended == 3) return &rtdata->data;
        else if (ended == 1) offset+=x;
        else return NULL;
        subnodes = ((COMPS_MRTreeData*)it->data)->subnodes;
    }
    if (it)
        return &((COMPS_MRTreeData*)it->data)->data;
    else return NULL;
}

COMPS_HSList ** comps_mrtree_getp(COMPS_MRTree * rt, const char * key) {
    COMPS_HSList * subnodes;
    COMPS_HSListItem * it = NULL;
    COMPS_MRTreeData * rtdata;
    unsigned int offset, len, x;
    char found, ended;

    len = strlen(key);
    offset = 0;
    subnodes = rt->subnodes;
    while (offset != len) {
        found = 0;
        for (it = subnodes->first; it != NULL; it=it->next) {
            if (((COMPS_MRTreeData*)it->data)->key[0] == key[offset]) {
                found = 1;
                break;
            }
        }
        if (!found)
            return NULL;
        rtdata = (COMPS_MRTreeData*)it->data;

        for (x=1; ;x++) {
            ended=0;
            if (rtdata->key[x] == 0) ended += 1;
            if (x == len - offset) ended += 2;
            if (ended != 0) break;
            if (key[offset+x] != rtdata->key[x]) break;
        }
        if (ended == 3) return &rtdata->data;
        else if (ended == 1) offset+=x;
        else return NULL;
        subnodes = ((COMPS_MRTreeData*)it->data)->subnodes;
    }
    if (it)
        return &((COMPS_MRTreeData*)it->data)->data;
    else return NULL;
}
