Reduce duplication in the pickPlatformItem helper function

Also, tweak code/comment used when handling "GoToR" destinations.

src/core/catalog.js

@@ -1628,18 +1628,20 @@ class Catalog {
               /* xref = */ null,
               /* skipContent = */ true
             );
-            const { rawFilename } = fs.serializable;
-            url = rawFilename;
+            ({ rawFilename: url } = fs.serializable);
           } else if (typeof urlDict === "string") {
             url = urlDict;
+          } else {
+            break;
           }
 
           // NOTE: the destination is relative to the *remote* document.
           const remoteDest = fetchRemoteDest(action);
-          if (remoteDest && typeof url === "string") {
+          if (remoteDest) {
             // NOTE: We don't use the `updateUrlHash` function here, since
-            // the `createValidAbsoluteUrl` function (see below) already
-            // handles parsing and validation of the final URL.
+            // the `createValidAbsoluteUrl` function (see below) already handles
+            // parsing/validation of the final URL and manual splitting also
+            // ensures that the `unsafeUrl` property will be available/correct.
             url = /* baseUrl = */ url.split("#", 1)[0] + "#" + remoteDest;
           }
           // The 'NewWindow' property, equal to `LinkTarget.BLANK`.

src/core/file_spec.js

@@ -18,21 +18,13 @@ import { BaseStream } from "./base_stream.js";
 import { Dict } from "./primitives.js";
 
 function pickPlatformItem(dict) {
-  if (!(dict instanceof Dict)) {
-    return null;
-  }
-  // Look for the filename in this order:
-  // UF, F, Unix, Mac, DOS
-  if (dict.has("UF")) {
-    return dict.get("UF");
-  } else if (dict.has("F")) {
-    return dict.get("F");
-  } else if (dict.has("Unix")) {
-    return dict.get("Unix");
-  } else if (dict.has("Mac")) {
-    return dict.get("Mac");
-  } else if (dict.has("DOS")) {
-    return dict.get("DOS");
+  if (dict instanceof Dict) {
+    // Look for the filename in this order: UF, F, Unix, Mac, DOS
+    for (const key of ["UF", "F", "Unix", "Mac", "DOS"]) {
+      if (dict.has(key)) {
+        return dict.get(key);
+      }
+    }
   }
   return null;
 }