Why IGMP parse don't set contents ?

[chrisFang5]

original hex stream:
[ 0x01, 0x00, 0x5e, 0x7f, 0xff, 0xfa, 0x00, 0x24, 0xe8, 0x7c, 0xbe, 0xd5, 0x08, 0x00, 0x46, 0x00, 0x00, 0x20, 0x73, 0xda, 0x00, 0x00, 0x01, 0x02, 0xee, 0x96, 0x0a, 0x00, 0xc8, 0x6c, 0xef, 0xff, 0xff, 0xfa, 0x94, 0x04, 0x00, 0x00, 0x12, 0x00, 0xfe, 0x04, 0xef, 0xff, 0xff, 0xfa, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00]

when I parsed and found that igmp contents is empty.
there is not assign data to contents in the IGMP(all version) code.
what's the rationale for doing so?

ps: i don't wanna get contents through ipv4's payload

here is output of parsed:

type:Ethernet
layerCon_Len:14, laypayload_len:46
layerCon:[1 0 94 127 255 250 0 36 232 124 190 213 8 0], laypayload:[70 0 0 32 115 218 0 0 1 2 238 150 10 0 200 108 239 255 255 250 148 4 0 0 18 0 254 4 239 255 255 250 0 0 0 0 0 0 0 0 0 0 0 0 0 0]

type:IPv4
layerCon_Len:24, laypayload_len:8
layerCon:[70 0 0 32 115 218 0 0 1 2 238 150 10 0 200 108 239 255 255 250 148 4 0 0], laypayload:[18 0 254 4 239 255 255 250]

type:IGMP
layerCon_Len:0, laypayload_len:0
layerCon:[], laypayload:[]
data:&{{[] []} IGMPv1 Membership Report 0s 65028 239.255.255.250 1}