Outline plugin fails to build on OBS

Tried my best at https://build.opensuse.org/package/show/home:Mailaender:branches:X11:Pantheon/scratch but I can't resolve this on my own:

scratch-2.0.2/plugins/outline/ValaSymbolResolver.vala:119.34-119.53: warning: GLib.Thread.create has been deprecated since 2.32. Use new Thread<T> ()
scratch-2.0.2/plugins/outline/ValaSymbolResolver.vala:120.4-120.22: warning: implicit .begin is deprecated
scratch-2.0.2/plugins/outline/ValaSymbolResolver.vala:119.34-122.10: warning: unhandled error `GLib.ThreadError'
scratch-2.0.2/plugins/outline/CtagsSymbolResolver.vala:173.50-173.66: warning: use of possibly unassigned parameter `parent'
 void parse_fields (string fields, out int line, out string parent)
                                                 ^^^^^^^^^^^^^^^^^
scratch-2.0.2/plugins/outline/CtagsSymbolResolver.vala:173.36-173.47: warning: use of possibly unassigned parameter `line'
 void parse_fields (string fields, out int line, out string parent)
                                   ^^^^^^^^^^^^
scratch-2.0.2/plugins/outline/ValaSymbolResolver.vala:124.3-124.8: error: duplicating Thread instance, use unowned variable or explicitly invoke copy method
  thread.join ();
  ^^^^^^
scratch-2.0.2/plugins/outline/ValaSymbolResolver.vala:124.3-124.8: error: duplicating Thread instance, use unowned variable or explicitly invoke copy method
  thread.join ();
  ^^^^^^

** (valac:3371): CRITICAL **: vala_ccode_base_module_get_cvalue_: assertion 'value != NULL' failed

** (valac:3371): CRITICAL **: vala_ccode_function_call_add_argument: assertion 'expr != NULL' failed
Compilation failed: 2 error(s), 5 warning(s)
make[2]: *** [plugins/outline/OutlinePlugin.c] Error 1
make[1]: *** [plugins/outline/CMakeFiles/outline.dir/all] Error 2