Remove extra commas in selectors

src/selector.rs

@@ -43,6 +43,17 @@ impl Display for Selector {
                         }
                     }
                 }
+                SelectorKind::Multiple => {
+                    devour_whitespace(&mut iter);
+                    while let Some(sel) = iter.peek() {
+                        if sel != &&SelectorKind::Multiple {
+                            write!(f, ", ")?;
+                            break;
+                        }
+                        iter.next();
+                        devour_whitespace(&mut iter);
+                    }
+                }
                 _ => write!(f, "{}", s)?,
             }
         }

tests/main.rs

@@ -309,6 +309,11 @@ mod test_selectors {
         "$x: oo, ba;\nf#{$x}r {\n  baz {\n    color: red;\n  }\n}\n",
         "foo baz, bar baz {\n  color: red;\n}\n"
     );
+    test!(
+        extra_commas,
+        "div,, , span, ,, {\n  color: red;\n}\n",
+        "div, span {\n  color: red;\n}\n"
+    );
 }
 
 #[cfg(test)]