Replace `ifNil:[...]` with `isNil ifTrue:[...]`
The latter is optimized by compilers and therefore faster.
"{ Package: 'stx:goodies/petitparser/compiler' }"
"{ NameSpace: Smalltalk }"
Warning subclass:#PPCCompilationWarning
instanceVariableNames:''
classVariableNames:''
poolDictionaries:''
category:'PetitCompiler-Exceptions'
!