Add a fallback for when the upload limit is undefined

0 is treated as falsy, ie. no limit is defined.
without setting a fallback, the produced config object is invalid as the key has no value, meaning that the grid client cannot launch

kahuna/app/views/main.scala.html

@@ -85,7 +85,7 @@
           permissionsDefault: "@kahunaConfig.permissionsDefault",
           defaultShouldBlurGraphicImages: @kahunaConfig.defaultShouldBlurGraphicImages,
           shouldUploadStraightToBucket: @kahunaConfig.shouldUploadStraightToBucket,
-          maybeUploadLimitInBytes: @kahunaConfig.maybeUploadLimitInBytes,
+          maybeUploadLimitInBytes: @kahunaConfig.maybeUploadLimitInBytes.getOrElse(0),
           announcements: @Html(announcements),
           imageTypes: @Html(imageTypes),
         }