Don't render href on nodes for unknown symbols for child relationships (#178)

* Don't render href on unknown symbols for child relationships

* Add changelog entry for #178

Co-authored-by: Mattt <mattt@me.com>

Author: MattKiazyk

Changelog.md

@@ -15,6 +15,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   #170 by @domcorvasce.
 - Fixed version number for swift-doc command.
   #159 by @mattt.
+- Fixed relationship diagram to prevent linking to unknown symbols.
+  #178 by @MattKiazyk.
 
 ## [1.0.0-beta.4] - 2020-07-31
 

Sources/swift-doc/Extensions/SwiftDoc+Extensions.swift

@@ -60,7 +60,10 @@ extension Symbol {
         for symbol in Set(relationships.flatMap { [$0.subject, $0.object] }) {
             guard self != symbol else { continue }
             var node = symbol.node
-            node.href = path(for: symbol, with: baseURL)
+
+            if !(symbol.api is Unknown) {
+                node.href = path(for: symbol, with: baseURL)
+            }
             graph.append(node)
         }