Add support for empty captcha images

src/Jackett/Content/index.html

@@ -165,7 +165,7 @@
         </div>
     </script>
     <script id="setup-item-displayimage" type="text/x-handlebars-template">
-        <img class="setup-item-displayimage" src="{{{value}}}" />
+        <img class="setup-item-displayimage" src="{{{value}}}" alt="No image available" />
     </script>
     <script id="setup-item-displayinfo" type="text/x-handlebars-template">
         <div class="setup-item-displayinfo alert alert-info" role="alert">{{{value}}}</div>

src/Jackett/Utils/DataUrl.cs

@@ -18,6 +18,8 @@ namespace Jackett.Utils
 
         public static string BytesToDataUrl(byte[] bytes, string mimeType = "image/jpg")
         {
+            if (bytes == null)
+                return null;
             return "data:" + mimeType + ";base64," + Convert.ToBase64String(bytes);
         }
     }