support null defaults

Author: baltzell

common-tools/clas-utils/src/main/java/org/jlab/utils/options/OptionValue.java

@@ -55,6 +55,6 @@ public boolean parse(List<String> arguments){
     }
 
     public boolean isDefault() {
-        return this.optionValue.equals(this.optionDefault);
+        return this.optionValue==null || this.optionValue.equals(this.optionDefault);
     }
 }