Add validation test for instances and color buffer

tests/validation/config.json

@@ -1017,6 +1017,11 @@
             "renderCount": 10,
             "playgroundId": "#MSAHKR#13",
             "referenceImage": "shadowsinstancesright.png"
+        },
+        {
+            "title": "Instances with color buffer",
+            "playgroundId": "#YPABS1#91",
+            "referenceImage": "instancecolors.png"
         }
     ]
 }

tests/validation/validation.js

@@ -104,7 +104,7 @@ async function evaluate(test, resultCanvas, result, renderImage, waitRing, done)
     var testRes = true;
 
     // gl check
-    var gl = engine._gl, glError = gl.getError();
+    var gl = engine._gl, glError = gl ? gl.getError() : 0;
     if (gl && glError !== 0) {
         result.classList.add("failed");
         result.innerHTML = "×";