Explicitly document that NavigationRegion.targets cannot be empty.

pkg/analysis_server/lib/src/generated_protocol.dart

Index: pkg/analysis_server/lib/src/generated_protocol.dart
diff --git a/pkg/analysis_server/lib/src/generated_protocol.dart b/pkg/analysis_server/lib/src/generated_protocol.dart
index 4ee4157b5f8fe071cc191b1eadcb55beebe5e306..672e029035dd652398b6b64b43b763485f080c02 100644
--- a/pkg/analysis_server/lib/src/generated_protocol.dart
+++ b/pkg/analysis_server/lib/src/generated_protocol.dart
@@ -11153,14 +11153,14 @@ class NavigationRegion implements HasToJson {
   /**
    * The indexes of the targets (in the enclosing navigation response) to which
    * the given region is bound. By opening the target, clients can implement
-   * one form of navigation.
+   * one form of navigation. This list cannot be empty.
    */
   List<int> get targets => _targets;
 
   /**
    * The indexes of the targets (in the enclosing navigation response) to which
    * the given region is bound. By opening the target, clients can implement
-   * one form of navigation.
+   * one form of navigation. This list cannot be empty.
    */
   void set targets(List<int> value) {
     assert(value != null);