[camera] Fix camera memory leak on IOS (#1745)

Needed to unregister the stream handler when disposing of the camera

Per the flutter documentation, the stream handler should be unregistered using setStreamHandler with nil.
https://api.flutter.dev/objcdoc/Classes/FlutterEventChannel.html#/c:objc(cs)FlutterEventChannel(im)setStreamHandler:

packages/camera/CHANGELOG.md

diff --git a/packages/camera/CHANGELOG.md b/packages/camera/CHANGELOG.md
index c096a9a..2d09af5 100644
--- a/packages/camera/CHANGELOG.md
+++ b/packages/camera/CHANGELOG.md
@@ -1,3 +1,7 @@
+## 0.5.2+2
+
+* Fix memory leak related to not unregistering stream handler in FlutterEventChannel when disposing camera.
+
 ## 0.5.2+1
 
 * Fix bug that prevented video recording with audio.

packages/camera/ios/Classes/CameraPlugin.m

diff --git a/packages/camera/ios/Classes/CameraPlugin.m b/packages/camera/ios/Classes/CameraPlugin.m
index 7bbd825..4c00192 100644
--- a/packages/camera/ios/Classes/CameraPlugin.m
+++ b/packages/camera/ios/Classes/CameraPlugin.m
@@ -456,6 +456,8 @@
 
 - (FlutterError *_Nullable)onCancelWithArguments:(id _Nullable)arguments {
   _eventSink = nil;
+  // need to unregister stream handler when disposing the camera
+  [_eventChannel setStreamHandler:nil];
   return nil;
 }
 

packages/camera/pubspec.yaml

diff --git a/packages/camera/pubspec.yaml b/packages/camera/pubspec.yaml
index 9aab9b9..a7e65c7 100644
--- a/packages/camera/pubspec.yaml
+++ b/packages/camera/pubspec.yaml
@@ -2,8 +2,8 @@
 description: A Flutter plugin for getting information about and controlling the
   camera on Android and iOS. Supports previewing the camera feed, capturing images, capturing video,
   and streaming image buffers to dart.
-version: 0.5.2+1
-publish_to: none
+version: 0.5.2+2
+
 authors:
   - Flutter Team <flutter-dev@googlegroups.com>
   - Luigi Agosti <luigi@tengio.com>