PeiGetVariable() and PeiGetNextVariableName() do not check NULL pointer access, not follow spec
[Impaction]
modify the Variable.c file in MdeModulePkg/Universal/Variable/Pei
[Reference Info]
PeiGetVariable() and PeiGetVariableName() do not follow spec
git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@4899 6f19259b-4bc3-4df7-8a09-765794883524