fixes #200, library prefixes for unknown imports

lib/src/utils.dart

Index: lib/src/utils.dart
diff --git a/lib/src/utils.dart b/lib/src/utils.dart
index 4c7339520c673f724b77c967c1d74164a4615bbe..9f21703d7deae66f079227fafa1807afc6f289ae 100644
--- a/lib/src/utils.dart
+++ b/lib/src/utils.dart
@@ -207,8 +207,15 @@ _MemberTypeGetter _memberTypeGetter(ExecutableElement member) {
   return f;
 }
 
-bool isDynamicTarget(Expression node) =>
-    node != null && !isLibraryPrefix(node) && node.staticType.isDynamic;
+bool isDynamicTarget(Expression node) {
+  if (node == null) return false;
+  var type = node.staticType;
+
+  // This is an unknown identifier, like an import that doesn't resolve.
+  if (type == null) return true;
+
+  return type.isDynamic && !isLibraryPrefix(node);
+}
 
 bool isLibraryPrefix(Expression node) =>
     node is SimpleIdentifier && node.staticElement is PrefixElement;