Webkit2gtk 2.40.5 is broken with the manager

[Bwc9876]

Upon upgrading to libwebkit2gtk 2.40.5, the manager opens a blank web view window and logs errors:

(on Nix):

EGLDisplay Initialization failed: EGL_BAD_ACCESS
Cannot create EGL sharing context: invalid display
Cannot create EGL context: invalid display

(on Arch):

libEGL warning: DRI3: Screen seems not DRI3 capable
libEGL warning: DRI2: failed to authenticate