Make sure when the backend cannot be downloaded or the site resolved that we're forgiving until we try to use the provided FFI functions.

private/racket-webview-downloader.rkt

@@ -4,6 +4,7 @@
          net/sendurl
          net/url
          net/url-connect
+         net/dns
          racket/file
          racket/system
          racket/string
@@ -15,6 +16,7 @@
          racket-webview-qt-directory
          racket-webview-qt-is-available?
          racket-webview-qt-is-downloadable?
+         racket-webview-qt-resolves?
          )
 
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
@@ -101,20 +103,30 @@
 
 (define (racket-webview-qt-directory)
   (if (racket-webview-qt-is-available?)
-      (build-path (format "~a/~a-~a" install-path rkt-qt-os rkt-qt-arch))
+      (build-path install-path (format "~a-~a" rkt-qt-os rkt-qt-arch))
       #f))
 
+(define (racket-webview-qt-resolves?)
+  (if (eq? (dns-find-nameserver) #f)
+    #f
+    (with-handlers ([exn:fail? (λ (e) #f)])
+      (dns-get-address (dns-find-nameserver) rkt-qt-download-site)
+      #t)
+    )
+  )
+
 (define (racket-webview-qt-version)
   (if (racket-webview-qt-is-available?)
       (file->value version-file)
       #f))
 
 (define (racket-webview-qt-is-downloadable?)
-  (let ((in (download-port rkt-download-url)))
-    (let ((d (input-port? in)))
-      (when d
-        (close-input-port in))
-      d)))
+  (with-handlers ([exn:fail? (λ (e) #f)])
+    (let ((in (download-port rkt-download-url)))
+      (let ((d (input-port? in)))
+        (when d
+          (close-input-port in))
+        d))))
 
 (define (download-racket-webview-qt)
   (let ((in (download-port rkt-download-url)))