ClojureScriptLanguage: decode unbound vars to null

This is common when, e.g., a script has no declared outputs, does not
assign a value to the "result" variable, and has no return value.

For example, the following script:

    (let [n 23] (println n))

was issuing the warning:

    [WARNING] Ignoring unsupported output: result [clojure.lang.Var$Unbound]

When really, the return value there should be null and hence ignored.

Author: ctrueden

src/main/java/org/scijava/plugins/scripting/clojure/ClojureScriptLanguage.java

@@ -40,6 +40,8 @@
 import org.scijava.script.AbstractScriptLanguage;
 import org.scijava.script.ScriptLanguage;
 
+import clojure.lang.Var;
+
 /**
  * An adapter of the Clojure interpreter to the SciJava scripting interface.
  * 
@@ -64,4 +66,9 @@ public ScriptEngine getScriptEngine() {
 		return new ClojureScriptEngine();
 	}
 
+	@Override
+	public Object decode(final Object object) {
+		if (object instanceof Var.Unbound) return null;
+		return object;
+	}
 }