Segfault in multipathd if multipath alias is missing from config file

Issue

• If there is a multipath {} stanza present in the configuration file that has a wwid specifier, and there is no alias defined, multipathd will segfault.
• Example configuration below:

       multipath {
                wwid    36k05076801je031cf0002000030003ba
                alias   disk1
        }
        multipath {
                wwid    360050768318e031f50000400000003bb   ##note missing alias
        }

• Core:

#0  0x0000003162878ca0 in strlen () from /lib64/libc.so.6
(gdb) where
#0  0x0000003162878ca0 in strlen () from /lib64/libc.so.6
#1  0x0000000000404bbf in check_mpe_alias () at config.c:142
#2  0x0000000000404e30 in load_config (file=0x4203b4 "/etc/multipath.conf") at config.c:520
#3  0x0000000000403057 in main (argc=2, argv=0x7fffade82f08) at main.c:343
(gdb) up
#1  0x0000000000404bbf in check_mpe_alias () at config.c:142
142         if (strlen(mpe->alias) > 5 && strlen(mpe->alias) < 16 &&
(gdb) p mpe
$1 = (struct mpentry *) 0x0