Change analysis server protocol to omit empty lists when optional.

editor/tools/plugins/com.google.dart.server/src/com/google/dart/server/generated/types/NavigationRegion.java

Index: editor/tools/plugins/com.google.dart.server/src/com/google/dart/server/generated/types/NavigationRegion.java
diff --git a/editor/tools/plugins/com.google.dart.server/src/com/google/dart/server/generated/types/NavigationRegion.java b/editor/tools/plugins/com.google.dart.server/src/com/google/dart/server/generated/types/NavigationRegion.java
index 17aef534c789491b4f834da4820c1b2a52282d86..061c105f3f7acc08dbd5224b11d8d7fee6aa9657 100644
--- a/editor/tools/plugins/com.google.dart.server/src/com/google/dart/server/generated/types/NavigationRegion.java
+++ b/editor/tools/plugins/com.google.dart.server/src/com/google/dart/server/generated/types/NavigationRegion.java
@@ -82,7 +82,7 @@ public class NavigationRegion {
   public static NavigationRegion fromJson(JsonObject jsonObject) {
     Integer offset = jsonObject.get("offset").getAsInt();
     Integer length = jsonObject.get("length").getAsInt();
-    List<Element> targets = Element.fromJsonArray(jsonObject.get("targets").getAsJsonArray());
+    List<Element> targets = jsonObject.get("targets") == null ? null : Element.fromJsonArray(jsonObject.get("targets").getAsJsonArray());
     return new NavigationRegion(offset, length, targets);
   }
 
@@ -124,11 +124,13 @@ public class NavigationRegion {
     JsonObject jsonObject = new JsonObject();
     jsonObject.addProperty("offset", offset);
     jsonObject.addProperty("length", length);
-    JsonArray jsonArrayTargets = new JsonArray();
-    for(Element elt : targets) {
-      jsonArrayTargets.add(elt.toJson());
+    if (targets != null) {
+      JsonArray jsonArrayTargets = new JsonArray();
+      for(Element elt : targets) {
+        jsonArrayTargets.add(elt.toJson());
+      }
+      jsonObject.add("targets", jsonArrayTargets);
     }
-    jsonObject.add("targets", jsonArrayTargets);
     return jsonObject;
   }