Making code more robust regarding scene being null in Character class

Not sure how this can happen but it does.
Closes #1167

front/src/Phaser/Entity/Character.ts

@@ -94,7 +94,7 @@ export abstract class Character extends Container {
 
     public addTextures(textures: string[], frame?: string | number): void {
         for (const texture of textures) {
-            if(!this.scene.textures.exists(texture)){
+            if(this.scene && !this.scene.textures.exists(texture)){
                 throw new TextureError('texture not found');
             }
             const sprite = new Sprite(this.scene, 0, 0, texture, frame);