Fixed a crashing bug in manifest content UI code
Fixed a crashing bug in manifest content UI code

MunkiAdmin would crash if manifest contained version referenced or non-existing items

hjuutilainen/munkiadmin,chrisgrande/munkiadmin,chrisgrande/munkiadmin,Tonyliu2ca/munkiadmin,Tonyliu2ca/munkiadmin,hjuutilainen/munkiadmin