I got the following error using P3.3.7, and updating just now to 3.5.2 did not help; the sketch did work in macOS 10.13.4- it printed the device enumeration warning, but did not crash as it does now; the sketch also runs without error on an RPi3 running the Processing 3.4 raspian distro:
GLVideo: Device enumeration is currently not available on macOS. The device returned is a pure guesstimate.
GLVideo: avfvideosrc0: Internal data stream error.
Debugging information: gstbasesrc.c(2939): void gst_base_src_loop(GstPad *) (): /GstPipeline:pipeline0/GstAVFVideoSrc:avfvideosrc0:
streaming stopped, reason not-negotiated (-4)