Fix pdnsrec for Linuxbrew
Fix pdnsrec for Linuxbrew

Fix the error: undefined method `<=' for nil:NilClass

maxim-belkin/homebrew-core,LinuxbrewTestBot/homebrew-core,LinuxbrewTestBot/homebrew-core,Linuxbrew/homebrew-core,rwhogg/homebrew-core,rwhogg/homebrew-core,Linuxbrew/homebrew-core,maxim-belkin/homebrew-core