[camerax] Fix _getResolutionSelectorFromPreset NPE (flutter#5287)

Fixes a mistake causing a NPE in `_getResolutionSelectorFromPreset`. Essentially, `boundSize` cannot be null except for one case (choosing the maximum available resolution), but the mistake I made was not allowing for that case to be valid.

(1/2 fixes really) Fixes flutter#135293.

Author: camsim99

packages/camera/camera_android_camerax/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 0.5.0+22
+
+* Fixes `_getResolutionSelectorFromPreset` null pointer error.
+
 ## 0.5.0+21
 
 * Changes fallback resolution strategies for camera use cases to look for a higher resolution if neither the desired

packages/camera/camera_android_camerax/lib/src/android_camera_camerax.dart

@@ -880,28 +880,30 @@ class AndroidCameraCameraX extends CameraPlatform {
         break;
       case ResolutionPreset.max:
         // Automatically set strategy to choose highest available.
-        resolutionStrategy = _shouldCreateDetachedObjectForTesting
-            ? ResolutionStrategy.detachedHighestAvailableStrategy()
-            : ResolutionStrategy.highestAvailableStrategy();
-        break;
+        if (_shouldCreateDetachedObjectForTesting) {
+          resolutionStrategy =
+              ResolutionStrategy.detachedHighestAvailableStrategy();
+          return ResolutionSelector.detached(
+              resolutionStrategy: resolutionStrategy);
+        }
+        resolutionStrategy = ResolutionStrategy.highestAvailableStrategy();
+        return ResolutionSelector(resolutionStrategy: resolutionStrategy);
       case null:
         // If no preset is specified, default to CameraX's default behavior
         // for each UseCase.
         return null;
     }
 
     if (_shouldCreateDetachedObjectForTesting) {
-      resolutionStrategy ??= ResolutionStrategy.detached(
+      resolutionStrategy = ResolutionStrategy.detached(
           boundSize: boundSize, fallbackRule: fallbackRule);
       return ResolutionSelector.detached(
           resolutionStrategy: resolutionStrategy);
     }
 
-    resolutionStrategy ??=
-        ResolutionStrategy(boundSize: boundSize!, fallbackRule: fallbackRule);
-    return ResolutionSelector(
-        resolutionStrategy: ResolutionStrategy(
-            boundSize: boundSize!, fallbackRule: fallbackRule));
+    resolutionStrategy =
+        ResolutionStrategy(boundSize: boundSize, fallbackRule: fallbackRule);
+    return ResolutionSelector(resolutionStrategy: resolutionStrategy);
   }
 
   /// Returns the [QualitySelector] that maps to the specified resolution

packages/camera/camera_android_camerax/pubspec.yaml

@@ -2,7 +2,7 @@ name: camera_android_camerax
 description: Android implementation of the camera plugin using the CameraX library.
 repository: https://github.com/flutter/packages/tree/main/packages/camera/camera_android_camerax
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+camera%22
-version: 0.5.0+21
+version: 0.5.0+22
 
 environment:
   sdk: ">=2.19.0 <4.0.0"