If constant pool index is equal to zero or constant pool entry at the index
is not a CONSTANT_Utf8_info structure as required in a class file then in
some cases JVM crashes while loading this class by Class.forName method call.

To reproduce run JCK tests:

tests/vm/classfmt/atr/atrlnt001/atrlnt00101/atrlnt00101.html
tests/vm/classfmt/atr/atrlnt002/atrlnt00201/atrlnt00201.html
tests/vm/classfmt/atr/atrlvt002/atrlvt00201/atrlvt00201.html
tests/vm/classfmt/atr/atrlvt003/atrlvt00301/atrlvt00301.html
tests/vm/classfmt/atr/atrnmi001/atrnmi00101/atrnmi00101.html
tests/vm/classfmt/mth/mthdsi001/mthdsi00102/mthdsi00102.html
tests/vm/classfmt/mth/mthdsi002/mthdsi00202/mthdsi00202.html
tests/vm/classfmt/mth/mthnmi001/mthnmi00101/mthnmi00101.html
tests/vm/classfmt/mth/mthnmi002/mthnmi00201/mthnmi00201.html
tests/vm/classfmt/mth/mthnmi002/mthnmi00202/mthnmi00202.html