Bail early in API analysis if no project is set.

lib/src/rules/package_api_docs.dart

Index: lib/src/rules/package_api_docs.dart
diff --git a/lib/src/rules/package_api_docs.dart b/lib/src/rules/package_api_docs.dart
index 0ee3e3482150e12da856ce9b69b09ab7e6146705..3a4966e32e666d0eafe2ad09b3443f8f6db69ca8 100644
--- a/lib/src/rules/package_api_docs.dart
+++ b/lib/src/rules/package_api_docs.dart
@@ -88,6 +88,11 @@ class Visitor extends GeneralizingAstVisitor {
   DartProject get project => rule.project;
 
   void check(Declaration node) {
+    // If no project info is set, bail early.
+    // https://github.com/dart-lang/linter/issues/154
+    if (project == null) {
+      return;
+    }
     if (project.isApi(node.element)) {
       if (node.documentationComment == null) {
         rule.reportLint(getNodeToAnnotate(node));