Allow empty paths when .catchalling (#146)

* Allow empty paths when `.catchall`ing

* Add check

* Add bug tracker to test

* Update test name

Author: ptoffy

Sources/RoutingKit/TrieRouter/TrieRouter.swift

@@ -95,6 +95,9 @@ public final class TrieRouter<Output: Sendable>: Router, Sendable, CustomStringC
         } else if let (catchall, subpaths) = currentCatchall {
             parameters.setCatchall(matched: subpaths)
             return catchall.output
+        } else if path.isEmpty, let catchall = currentNode.catchall {
+            parameters.setCatchall(matched: [])
+            return catchall.output
         } else {
             return nil
         }

Tests/RoutingKitTests/RouterTests.swift

@@ -382,4 +382,14 @@ struct RouterTests {
         p = Parameters()
         #expect(r.route(path: ["y", "file.md"], parameters: &p) == 1)
     }
+
+    @Test("Catchall catches empty path", .bug("https://github.com/vapor/routing-kit/issues/147"))
+    func emptyCatchall() throws {
+        var b = TrieRouterBuilder<Int>()
+        b.register(1, at: [.catchall])
+        let r = b.build()
+
+        var p = Parameters()
+        #expect(r.route(path: [], parameters: &p) == 1)
+    }
 }