Cannot use `camera` component on `<a-mixin>`

[mattrossman]

Description: Using the camera component on <a-mixin> causes a perpetual loading screen

• A-Frame Version: 1.3.0
• Platform / Device: Windows 10
• Reproducible Code Snippet or URL: https://jsfiddle.net/mattrossman/rsw2m7j9/1/

Additional Info:

looks like a bug. 90% sure is that a querySelector is picking up the mixin by mistake

aframe/src/systems/camera.js

Line 178 in b164623

cameraEls = sceneEl.querySelectorAll('[camera]');

(view on Discord)