fix: Size for SpriteComponent.fromImage should be nullable (#3054)

I received an assertion error after I set `autoResize` to true when I am
using `SpriteComponent.fromImage` component. It's kinda weird for me
that the message tells me **"If size is set, autoResize should be false
or size should be null when autoResize is true.''**, but the thing is I
never set the size for that image yet. Then, I check the code and I
found out that the size will never be null anyway, so the `autoresize`
should always be false.

In this PR, I just remove all the fallback value for `size`, so it would
not give an assertion error when `size` is not being set yet while the
`autoresize` is true.

---------

Co-authored-by: Lukas Klingsbo <me@lukas.fyi>

packages/flame/lib/src/components/sprite_component.dart

@@ -2,7 +2,6 @@ import 'dart:ui';
 
 import 'package:flame/components.dart';
 import 'package:flame/src/effects/provider_interfaces.dart';
-import 'package:flame/src/extensions/image.dart';
 import 'package:meta/meta.dart';
 
 export '../sprite.dart';
@@ -75,7 +74,7 @@ class SpriteComponent extends PositionComponent
           autoResize: autoResize,
           paint: paint,
           position: position,
-          size: size ?? srcSize ?? image.size,
+          size: size,
           scale: scale,
           angle: angle,
           anchor: anchor,

packages/flame/test/components/sprite_component_test.dart

@@ -44,8 +44,20 @@ Future<void> main() async {
         () => SpriteComponent(autoResize: true, size: Vector2.all(2)),
         throwsAssertionError,
       );
+      expect(
+        () => SpriteComponent.fromImage(
+          image,
+          autoResize: true,
+          size: Vector2.all(2),
+        ),
+        throwsAssertionError,
+      );
 
       expect(() => SpriteComponent(autoResize: false), throwsAssertionError);
+      expect(
+        () => SpriteComponent.fromImage(image, autoResize: false),
+        throwsAssertionError,
+      );
     });
 
     test('default value set correctly when not provided explicitly', () {