Sigtest doesn't work well with default values for Deprecated annotaion

When sigtest is used with the options below the following is the result for Deprecated annotation:
 anno 0 java.lang.Deprecated(boolean forRemoval=null, java.lang.String since=null)

Expected with default values:
 anno 0 java.lang.Deprecated(boolean forRemoval=false, java.lang.String since="")


To reproduce:

/set/java/re/jdk/9/promoted/ea/123/binaries/solaris-sparcv9/bin/java -classpath /net/fury.ru.oracle.com/export/users/vrudomet/9/build_reviewed/out/shared/suite/JCK-compiler-9/classes com.sun.tdk.signaturetest.Setup -fileName result.sig -classpath 1/:1/javase9_java.sig -static -NonClosedFile -package Vitek

Files attached.