fix(transformers): replace an error with a warning when cannot resolve a symbol

modules_dart/transform/lib/src/transform/template_compiler/compile_data_creator.dart

@@ -235,7 +235,7 @@ class _CompileDataCreator {
       return new CompileIdentifierMetadata(name: "FiberMarket", moduleUrl: 'unspecified');
 
     } else {
-      log.error(
+      log.warning(
           'Missing identifier "${id.name}" '
               'needed by "${neededBy.name}" from metadata map',
           asset: entryPoint);