Product Version: NetBeans IDE Dev (Build 201504270341)
Java: 1.8.0_45; Java HotSpot(TM) 64-Bit Server VM 25.45-b02
Runtime: Java(TM) SE Runtime Environment 1.8.0_45-b14
System: Windows 7 version 6.1 running on amd64; UTF-8; pl_PL (nb)

Values displayed in tooltips for null member variables are incorrect. Looks like they show information about "this" instead of the variable.

Test case:

public class NullMember {

    String text;
    String dummy = "";

    public NullMember() {
    }

    public String doNothing() {
        String localNull = null;
        for (int i = 1; i < 10; i++) {
            if (text == null) {
                dummy += i;
            } else {
                dummy += text;
                localNull += this;
            }
        }
        return localNull;
    }

//    @Override
//    public String toString() {
//        return "Dummy is " + dummy;
//    }

}

Put a breakpoint in the "doNothing" method. Hover over "text" variable - it will show "package.name.NullMember@1175e2db" instead of simply "null.
Uncomment the "toString" method and it will become even more interesting - tooltip for "text" will show "Dummy is " instead of null.