feat: Make cameras optional (#2343)

src/card-controller/view/modifiers/substream-on.ts

@@ -15,6 +15,10 @@ export class SubstreamOnViewModifier implements ViewModifier {
   }
 
   public modify(view: View): void {
+    if (!view.camera) {
+      return;
+    }
+
     const dependencies = [
       ...this._api
         .getCameraManager()
@@ -27,6 +31,13 @@ export class SubstreamOnViewModifier implements ViewModifier {
     }
 
     const currentOverride = getStreamCameraID(view);
+
+    /* istanbul ignore if: the if path cannot be reached, as there is a
+    view.camera guard at the start of this method and getStreamCameraID will
+    always return non-null as long as camera is present -- @preserve */
+    if (!currentOverride) {
+      return;
+    }
     const currentIndex = dependencies.indexOf(currentOverride);
     const newIndex = currentIndex < 0 ? 0 : (currentIndex + 1) % dependencies.length;