javap should be more robust in the face of invalid class files

Below is an example of how javap fails when run to disassemble a class file with a Signature attribute with an index into the constant pool of the wrong type. In this example it would have been useful if javap reported the reason why it could not parse the the class file.

Error: A serious internal error has occurred: java.lang.IllegalStateException: !'!, '
Please file a bug report, and include the following information:
java.lang.IllegalStateException: !'!, '
    at jdk.jdeps/com.sun.tools.classfile.Signature.parseTypeSignature(Signature.java:180)
    at jdk.jdeps/com.sun.tools.classfile.Signature.parse(Signature.java:104)
    at jdk.jdeps/com.sun.tools.classfile.Signature.getType(Signature.java:48)
    at jdk.jdeps/com.sun.tools.javap.ClassWriter.writeMethod(ClassWriter.java:499)
    at jdk.jdeps/com.sun.tools.javap.ClassWriter.writeMethods(ClassWriter.java:471)
    at jdk.jdeps/com.sun.tools.javap.ClassWriter.write(ClassWriter.java:269)
    at jdk.jdeps/com.sun.tools.javap.JavapTask.write(JavapTask.java:850)
    at jdk.jdeps/com.sun.tools.javap.JavapTask.writeClass(JavapTask.java:669)
    at jdk.jdeps/com.sun.tools.javap.JavapTask.run(JavapTask.java:614)
    at jdk.jdeps/com.sun.tools.javap.JavapTask.run(JavapTask.java:464)
    at jdk.jdeps/com.sun.tools.javap.Main.main(Main.java:47)