Fix curve with multiple non-closed components. (#5963)

crates/typst-layout/src/shapes.rs

@@ -284,6 +284,7 @@ impl<'a> CurveBuilder<'a> {
         self.last_point = point;
         self.last_control_from = point;
         self.is_started = true;
+        self.is_empty = true;
     }
 
     /// Add a line segment.

tests/suite/visualize/curve.typ

@@ -38,6 +38,16 @@
   curve.close(mode: "smooth"),
 )
 
+--- curve-multiple-non-closed ---
+#curve(
+  stroke: 2pt,
+  curve.line((20pt, 0pt)),
+  curve.move((0pt,  10pt)),
+  curve.line((20pt, 10pt)),
+  curve.move((0pt,  20pt)),
+  curve.line((20pt, 20pt)),
+)
+
 --- curve-line ---
 #curve(
   fill: purple,