Work around a crash on the intersection demand panel, reproducible by

watching https://www.openstreetmap.org/node/53214134 on the weekday
scenario. At some point, an arrow polygon with an inner ring is scaled
down, collapsing its points so much that the ring becomes invalid.

ezgui/src/geom.rs

@@ -195,7 +195,9 @@ impl GeomBatch {
             return self;
         }
         for (_, poly) in &mut self.list {
-            *poly = poly.scale(factor);
+            // strip_rings first -- sometimes when scaling down, the original rings collapse. Since
+            // this polygon is part of a GeomBatch anyway, not calling to_outline on it.
+            *poly = poly.strip_rings().scale(factor);
         }
         self
     }

geom/src/polygon.rs

@@ -307,6 +307,14 @@ impl Polygon {
         }
     }
 
+    // Remove the internal rings used for to_outline. This is fine to do if the polygon is being
+    // added to some larger piece of geometry that won't need an outline.
+    pub fn strip_rings(&self) -> Polygon {
+        let mut p = self.clone();
+        p.rings = None;
+        p
+    }
+
     // Usually m^2, unless the polygon is in screen-space
     pub fn area(&self) -> f64 {
         // Polygon orientation messes this up sometimes