fix(renderer): guard ImageManager callback against use-after-free (#4233)

test/style/source.test.cpp

@@ -63,7 +63,7 @@ public:
     Transform transform;
     TransformState transformState;
     AnnotationManager annotationManager{style};
-    std::shared_ptr<ImageManager> imageManager = std::make_shared<ImageManager>();
+    std::shared_ptr<ImageManager> imageManager = ImageManager::create();
     std::shared_ptr<GlyphManager> glyphManager = std::make_shared<GlyphManager>();
     gfx::DynamicTextureAtlasPtr dynamicTextureAtlas;
     TaggedScheduler threadPool;