Bug 1579374 - Show information when mediacapabilities folder doesn't exist in the profile yet. r=chunmin

When the mediacapabilities folder does not exist catch the exception and print the name of the decoder.

Differential Revision: https://phabricator.services.mozilla.com/D45352

--HG--
extra : moz-landing-system : lando

toolkit/content/aboutSupport.js

@@ -889,6 +889,9 @@ var snapshotFormatters = {
                 }
                 $("enumerate-database-result").textContent +=
                   logs.join("\n") + "\n";
+              })
+              .catch(err => {
+                $("enumerate-database-result").textContent += `${name}:\n`;
               });
           }