Crash when opening google photo login page

Hello,

this is a forwarded bug from Debian[1]:

Package: shotwell
Version: 0.30.4-1
Severity: normal

Steps to reproduce:
- select an image
- click on "Publish"
- the publish dialog opens... choose "Google Photos"
- click the "Log in" button
-> Segmentation fault

A backtrace gives:
#0  0x00007fffd5c0cc9b in  () at /usr/lib/x86_64-linux-gnu/libshotwell-authenticator.so.0
#1  0x00007ffff7d8bc7d in g_closure_invoke () at /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#2  0x00007ffff7d9f345 in  () at /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#3  0x00007ffff7da825e in g_signal_emit_valist () at /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#4  0x00007ffff7da891f in g_signal_emit () at /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#5  0x00007fffe4b8d4b5 in  () at /usr/lib/x86_64-linux-gnu/libwebkit2gtk-4.0.so.37
#6  0x00007fffe4b6e567 in  () at /usr/lib/x86_64-linux-gnu/libwebkit2gtk-4.0.so.37
#7  0x00007fffe4984cbb in  () at /usr/lib/x86_64-linux-gnu/libwebkit2gtk-4.0.so.37
#8  0x00007fffe4cbbb71 in  () at /usr/lib/x86_64-linux-gnu/libwebkit2gtk-4.0.so.37
#9  0x00007fffe4cb3e74 in  () at /usr/lib/x86_64-linux-gnu/libwebkit2gtk-4.0.so.37
#10 0x00007fffe48f9409 in  () at /usr/lib/x86_64-linux-gnu/libwebkit2gtk-4.0.so.37
#11 0x00007fffe49b3082 in  () at /usr/lib/x86_64-linux-gnu/libwebkit2gtk-4.0.so.37
#12 0x00007fffe48f4fab in  () at /usr/lib/x86_64-linux-gnu/libwebkit2gtk-4.0.so.37
#13 0x00007fffe48f5bd8 in  () at /usr/lib/x86_64-linux-gnu/libwebkit2gtk-4.0.so.37
#14 0x00007fffd9ca7115 in WTF::RunLoop::performWork() () at /usr/lib/x86_64-linux-gnu/libjavascriptcoregtk-4.0.so.18
#15 0x00007fffd9ca5fc9 in  () at /usr/lib/x86_64-linux-gnu/libjavascriptcoregtk-4.0.so.18
#16 0x00007ffff7ca9dd8 in g_main_context_dispatch () at /usr/lib/x86_64-linux-gnu/libglib-2.0.so.0
#17 0x00007ffff7caa1c8 in  () at /usr/lib/x86_64-linux-gnu/libglib-2.0.so.0
#18 0x00007ffff7caa4c2 in g_main_loop_run () at /usr/lib/x86_64-linux-gnu/libglib-2.0.so.0
#19 0x00007ffff7139583 in gtk_dialog_run () at /usr/lib/x86_64-linux-gnu/libgtk-3.so.0
#20 0x0000555555645fbf in publishing_ui_publishing_dialog_run ()
#21 0x00005555556461f5 in publishing_ui_publishing_dialog_go ()

and

Compiling from source and running in gdb, the crash happens in
    plugins/authenticator/shotwell/GoogleAuthenticator.vala:25
In line 24, the variable uri is defined as:
    new Soup.URI(get_view().get_uri())
but get_view().get_uri() turns out to be null,

Running with logging (SHOTWELL_LOG=1 SHOTWELL_LOG_FILE=:console:), I get:
L 22817 2019-08-14 02:30:27 [DBG] PublishingPluginHost.vala:113:
ConcretePublishingHost.start_publishing( ): invoked.
L 22817 2019-08-14 02:30:27 [DBG] PhotosPublisher.vala:525:
GooglePhotos.Publisher: start() invoked.
L 22817 2019-08-14 02:30:27 [DBG] GoogleAuthenticator.vala:421:
ACTION: showing service welcome pane.
L 22817 2019-08-14 02:30:27 [DBG] PublishingUI.vala:542:
PublishingDialog: install_pane( ): invoked.
L 22817 2019-08-14 02:30:35 [DBG] GoogleAuthenticator.vala:427: EVENT:
user clicked 'Login' in welcome pane.
L 22817 2019-08-14 02:30:35 [DBG] GoogleAuthenticator.vala:167:
ACTION: running OAuth authentication flow in hosted web pane.
L 22817 2019-08-14 02:30:35 [DBG] PublishingPluginHost.vala:70:
Publishing.PluginHost: install_dialog_pane( ): invoked.
L 22817 2019-08-14 02:30:35 [DBG] PublishingUI.vala:542:
PublishingDialog: install_pane( ): invoked.
L 22817 2019-08-14 02:30:35 [DBG] PublishingUI.vala:545:
PublishingDialog: install_pane( ): a pane is already installed;
removing it.
Segmentation fault

CU Jörg Frings-Fürst

[1] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=934723