fix: loosen Engine.start('scene', {loader}) signature

CHANGELOG.md

@@ -70,6 +70,7 @@ are doing mtv adjustments during precollision.
 
 ### Fixed
 
+- Fixed issue where you were required to provide a transition if you provided a loader in the `ex.Engine.start('scene', { loader })`
 - Fixed issue where `ex.Scene.onPreLoad(loader: ex.DefaultLoader)` would lock up the engine if there was an empty loader
 - Fixed issue where `ex.Scene` scoped input events would preserve state and get stuck causing issues when switching back to the original scene.
 - Fixed issue where not all physical keys from the spec were present in `ex.Keys` including the reported `ex.Keys.Tab`

src/engine/Director/Director.ts

@@ -58,9 +58,9 @@ export type SceneMap<TKnownScenes extends string = any> = Record<TKnownScenes, S
 
 export interface StartOptions {
   /**
-   * First transition from the game start screen
+   * Optionally provide first transition from the game start screen
    */
-  inTransition: Transition;
+  inTransition?: Transition;
   /**
    * Optionally provide a main loader to run before the game starts
    */
@@ -215,7 +215,7 @@ export class Director<TKnownScenes extends string = any> {
 
     let maybeStartTransition: Transition;
 
-    if (options) {
+    if (options?.inTransition) {
       const { inTransition } = options;
       maybeStartTransition = inTransition;
     }