Fix NPT when visiting qualifier in property access

compiler/java/com/google/dart/compiler/ast/DartToSourceVisitor.java

Index: compiler/java/com/google/dart/compiler/ast/DartToSourceVisitor.java
===================================================================
--- compiler/java/com/google/dart/compiler/ast/DartToSourceVisitor.java	(revision 13091)
+++ compiler/java/com/google/dart/compiler/ast/DartToSourceVisitor.java	(working copy)
@@ -673,7 +673,9 @@
 
   @Override
   public Void visitPropertyAccess(DartPropertyAccess x) {
-    accept(x.getQualifier());
+    if (x.getQualifier() != null) {
+      accept(x.getQualifier());

[Brian Wilkerson, 2012/10/02 13:14:23]

It might have been better for the invocation of 'accept' to go into the 'else'
clause below (without the surrounding 'if'). The qualifier should only be null
if it is part of a cascade section, and that would have made the semantics more
clear.

+    }
     if (x.isCascade()) {
       p("..");
     } else {