Using the latest code from the git repository and Firefox 51.0.1, visiting a protected site (e.g.
http://ftfl.ca/bm) fails and no login prompt is displayed.

Terminal output when visiting such a site:

JavaScript error: resource://gre/components/nsLoginManagerPrompter.js, line 1373: TypeError: win.gBrowser
is undefined
JavaScript error: , line 0: uncaught exception: 2147500033
JavaScript error: resource://gre/components/nsPrompter.js, line 741: TypeError: checkValue is undefined
Console error: [JavaScript Error: "TypeError: win.gBrowser is undefined" {file:
"resource://gre/components/nsLoginManagerPrompter.js" line: 1373}]
  Category: chrome javascript
Console error: [JavaScript Error: "nsPrompter: Delegation to password manager failed: [Exception...
"[JavaScript Error: "win.gBrowser is undefined" {file:
"resource://gre/components/nsLoginManagerPrompter.js" line: 1373}]'[JavaScript Error: "win.gBrowser is
undefined" {file: "resource://gre/components/nsLoginManagerPrompter.js" line: 1373}]' when calling
method: [nsIPromptFactory::getPrompt]"  nsresult: "0x80570021
(NS_ERROR_XPC_JAVASCRIPT_ERROR_WITH_DETAILS)"  location: "JS frame ::
resource://gre/components/nsPrompter.js :: Prompter.prototype.getPrompt :: line 42"  data: yes]" {file:
"resource://gre/components/nsPrompter.js" line: 44}]
Prompter.prototype.getPrompt@resource://gre/components/nsPrompter.js:44:17

  Category: XPConnect JavaScript
Console error: [JavaScript Error: "uncaught exception: 2147500033"]
  Category: chrome javascript
Console error: [JavaScript Error: "TypeError: checkValue is undefined" {file:
"resource://gre/components/nsPrompter.js" line: 741}]
  Category: chrome javascript
Console error: [JavaScript Error: "The character encoding of the HTML document was not declared. The
document will render with garbledtext in some browser configurations if the document contains characters
from outside the US-ASCII range. The character encoding of thepage must be declared in the document or in
the transfer protocol." {file: "https://ftfl.ca/bm" line: 0}]
  Category: HTML parser
Console error: [JavaScript Warning: "Warning: nsFaviconService::setAndFetchFaviconForPage() deprecated,
please use nsFaviconService::setAndFetchFaviconForPage(..., [optional aLoadingPrincipal])" {file:
"chrome://conkeror/content/favicon.js" line: 24}]
  Category: Security by Default