small fix in RInstrumentation

com.oracle.truffle.r.nodes/src/com/oracle/truffle/r/nodes/instrumentation/RInstrumentation.java

@@ -54,7 +54,7 @@ public class RInstrumentation {
     }
 
     public static SourceSection getSourceSection(RFunction func) {
-        return getFunctionDefinitionNode(func).getSourceSection();
+        return func.getRootNode().getSourceSection();
     }
 
     /**