render_json: Make compatible with stable nvisii version

Without this commit, render_json will only work with the development
version of nvisii, not the one from pip.

scripts/metrics/render_json.py

@@ -162,7 +162,15 @@ def create_obj(
 visii.set_camera_entity(camera)
 
 visii.set_dome_light_intensity(1)
-visii.set_dome_light_color(visii.vec3(1,1,1),0)
+
+try:
+    visii.set_dome_light_color(visii.vec3(1, 1, 1), 0)
+except TypeError:
+    # Support for alpha transparent backgrounds was added in nvisii ef1880aa,
+    # but as of 2022-11-03, the latest released version (1.1) does not include
+    # that change yet.
+    print("WARNING! Your version of NVISII does not support alpha transparent backgrounds yet; --contour will not work properly.")
+    visii.set_dome_light_color(visii.vec3(1, 1, 1))
 
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