Fix panic for tiny anti-aliased rectangles (#119)

Author: nwhitehead

src/scan/hairline_aa.rs

@@ -120,8 +120,6 @@ fn fill_dot8(l: FDot8, t: FDot8, r: FDot8, b: FDot8, fill_inner: bool, blitter:
                     } else {
                         debug_assert!(false);
                     }
-                } else {
-                    debug_assert!(false);
                 }
             }
 

tests/integration/fill.rs

@@ -187,6 +187,16 @@ fn tiny_float_rect_aa() {
     );
 }
 
+#[test]
+fn tiny_rect_aa() {
+    let mut paint = Paint::default();
+    paint.set_color_rgba8(0, 0, 0, 0);
+    paint.anti_alias = true;
+    let rect = Rect::from_xywh(0.7, 0.0, 1.0, 2.0).unwrap();
+    let mut pixmap = Pixmap::new(10, 10).unwrap();
+    pixmap.fill_rect(rect, &paint, Transform::identity(), None);
+}
+
 #[test]
 fn float_rect_clip_top_left_aa() {
     let mut paint = Paint::default();