Make package mime strong clean

test/mime_type_test.dart

Index: test/mime_type_test.dart
diff --git a/test/mime_type_test.dart b/test/mime_type_test.dart
index 0ac32f5860852dfe5c7aa3d59c65325f5cae93b1..87de96df35070f1e4e80935c654bf1999038cdc1 100644
--- a/test/mime_type_test.dart
+++ b/test/mime_type_test.dart
@@ -93,7 +93,7 @@ void main() {
   });
 
   test('default magic number', () {
-    var actualMaxBytes = DEFAULT_MAGIC_NUMBERS.fold(0, (previous, magic) {
+    var actualMaxBytes = DEFAULT_MAGIC_NUMBERS.fold(0, (num previous, magic) {
       return math.max(previous, magic.numbers.length);
     });