Address comment from 55981

Change-Id: I8e0e95239f613d15d130c465a0d39dd04a044194
Reviewed-on: https://dart-review.googlesource.com/56200
Reviewed-by: Dan Rubel <danrubel@google.com>
Commit-Queue: Brian Wilkerson <brianwilkerson@google.com>
diff --git a/pkg/front_end/lib/src/fasta/kernel/body_builder.dart b/pkg/front_end/lib/src/fasta/kernel/body_builder.dart
index abbbb39..abcc818 100644
--- a/pkg/front_end/lib/src/fasta/kernel/body_builder.dart
+++ b/pkg/front_end/lib/src/fasta/kernel/body_builder.dart
@@ -2320,14 +2320,11 @@
       optional = pop();
       count--;
     }
-    FormalParameters<Arguments> formals = new FormalParameters(
-        popList(
-                count,
-                new List<VariableDeclaration>.filled(count, null,
-                    growable: true)) ??
-            <VariableDeclaration>[],
-        optional,
-        beginToken.charOffset);
+    List<VariableDeclaration> variables =
+        new List<VariableDeclaration>.filled(count, null, growable: true);
+    popList(count, variables);
+    FormalParameters<Arguments> formals =
+        new FormalParameters(variables, optional, beginToken.charOffset);
     constantContext = pop();
     push(formals);
     if ((inCatchClause || functionNestingLevel != 0) &&