gpu/internal/rendertest: allow nil pixel check functions

Signed-off-by: Elias Naur <mail@eliasnaur.com>

gpu/internal/rendertest/clip_test.go

@@ -132,8 +132,7 @@ func TestTexturedStrokeClipped(t *testing.T) {
 		defer clip.RRect{Rect: image.Rect(-30, -30, 60, 60)}.Push(o).Pop()
 		defer op.Offset(image.Pt(-10, -10)).Push(o).Pop()
 		paint.PaintOp{}.Add(o)
-	}, func(r result) {
-	})
+	}, nil)
 }
 
 func TestTexturedStroke(t *testing.T) {
@@ -146,8 +145,7 @@ func TestTexturedStroke(t *testing.T) {
 		}.Op().Push(o).Pop()
 		defer op.Offset(image.Pt(-10, -10)).Push(o).Pop()
 		paint.PaintOp{}.Add(o)
-	}, func(r result) {
-	})
+	}, nil)
 }
 
 func TestPaintClippedTexture(t *testing.T) {
@@ -252,8 +250,7 @@ func TestPathReuse(t *testing.T) {
 		stroke := clip.Stroke{Path: spec, Width: 3}.Op().Push(o)
 		paint.Fill(o, color.NRGBA{B: 0xFF, A: 0xFF})
 		stroke.Pop()
-	}, func(r result) {
-	})
+	}, nil)
 }
 
 func TestPathInterleave(t *testing.T) {
@@ -290,8 +287,7 @@ func TestStrokedRect(t *testing.T) {
 				Width: 5,
 			}.Op(),
 		)
-	}, func(r result) {
-	})
+	}, nil)
 }
 
 func TestInstancedRects(t *testing.T) {