elf: Check if PT_INTERP entry exists
elf: Check if PT_INTERP entry exists

Not every ELF file has a PT_INTERP enty. This commit will catch a
potential AttributeError if no PT_INTERP entry is found.

postfix/viper-1,MeteorAdminz/viper,jahrome/viper,jorik041/viper,kevthehermit/viper,Beercow/viper,jahrome/viper,postfix/viper-1,S2R2/viper,cwtaylor/viper,Beercow/viper,MeteorAdminz/viper,jack51706/viper,jack51706/viper,kevthehermit/viper,S2R2/viper,cwtaylor/viper,jorik041/viper,Beercow/viper