pelican-bootstrap3: Display navbar-toggle button only if pages exist and DISPLAY_PAGES_ON_MENU is enabled or categories exist and DISPLAY_CATEGORIES_ON_MENU is enabled.
pelican-bootstrap3: Display navbar-toggle button
only if pages exist and DISPLAY_PAGES_ON_MENU is
enabled or categories exist and
DISPLAY_CATEGORIES_ON_MENU is enabled.

Cherry picked from commit
getpelican/pelican-themes@77af0b69c30fe5c23e72b3ec0a1e362c140968f0.

StevenMaude/pelican-bootstrap3-sm,StevenMaude/pelican-bootstrap3-sm