Bug report: NPE in DebugLogger.levelAbove

[Tal Liron]

The code uses Logger.getLevel(), but doesn't take into account that the 
value could be null. Exception trace:

java.lang.NullPointerException
    at 
jdk.nashorn.internal.runtime.DebugLogger.levelAbove(DebugLogger.java:129)
    at jdk.nashorn.internal.codegen.Compiler.compile(Compiler.java:352)
    at jdk.nashorn.internal.runtime.Context.compile(Context.java:887)
    at jdk.nashorn.internal.runtime.Context.compileScript(Context.java:844)
    at jdk.nashorn.internal.runtime.Context.compileScript(Context.java:387)