fix: --reporter=json for check-unnecessary-nullable crashes, saying Converting object to an encodable object failed: Instance of 'MappedIterable<FormalParameter, String>' (#980)

* fix --reporter=json for check-unnecessary-nullable crashes, saying Converting object to an encodable object failed: Instance of 'MappedIterable<FormalParameter, String>' #979

* Update CHANGELOG.md

Author: fzyzcjy

CHANGELOG.md

@@ -4,6 +4,7 @@
 
 * feat: support passing file paths to all commands.
 * fix: avoid-top-level-members-in-tests ignore lib
+* fix: `--reporter=json` for `check-unnecessary-nullable` crashes, saying `Converting object to an encodable object failed: Instance of 'MappedIterable<FormalParameter, String>'`
 
 ## 4.18.0-dev.2
 

lib/src/analyzers/unnecessary_nullable_analyzer/reporters/reporters_list/json/unnecessary_nullable_json_reporter.dart

@@ -44,7 +44,7 @@ class UnnecessaryNullableJsonReporter extends JsonReporter<
   Map<String, Object> _issueToJson(UnnecessaryNullableIssue issue) => {
         'declarationType': issue.declarationType,
         'declarationName': issue.declarationName,
-        'parameters': issue.parameters,
+        'parameters': issue.parameters.toList(),
         'column': issue.location.column,
         'line': issue.location.line,
         'offset': issue.location.offset,