Dashboard crashes when Proposals are deleted due to ActiveLog

[tramuntanal]

Describe the bug
The problem is that proposal drafts can be removed, but the Admin Activity Log, when renders Proposals takes for granted that the associated resource, when a Proposal, there's always there. But this is not always true.

Culprit: Admin Log (rendered in the Dashboard and in the Admin Activity Log).

The crash raises in Decidim::Proposals::ProposalPresenter.title:L44 with the typical "no title method for Nil class" message.

To Reproduce
Steps to reproduce the behavior:

1. Go to 'a participatory process'
2. Enable participatory text
3. import a document
4. discard the participatory text
5. go to dashboard or AdminLog

Expected behavior
ActionLog should not crash when proposals are discarded.

Stacktrace

F, [2019-07-10T09:29:35.769851 #3089] FATAL -- : ActionView::Template::Error (undefined method `title' for nil:NilClass):
F, [2019-07-10T09:29:35.769971 #3089] FATAL -- :      8:     <% if logs.any? %>
     9:       <ul class="logs table">
    10:         <% logs.each do |log| %>
    11:           <%= render_log(log) %>
    12:         <% end %>
    13:       </ul>
    14:     <% else %>
F, [2019-07-10T09:29:35.770004 #3089] FATAL -- :
F, [2019-07-10T09:29:35.770053 #3089] FATAL -- : /home/decidim/.rvm/gems/ruby-2.5.3/bundler/gems/decidim-88bdce57dd9a/decidim-proposals/app/presenters/decidim/proposals/proposal_presenter.rb:44:in `title'
/home/decidim/.rvm/gems/ruby-2.5.3/bundler/gems/decidim-88bdce57dd9a/decidim-proposals/app/presenters/decidim/proposals/log/resource_presenter.rb:13:in `present_resource_name'
/home/decidim/.rvm/gems/ruby-2.5.3/bundler/gems/decidim-88bdce57dd9a/decidim-core/app/presenters/decidim/log/resource_presenter.rb:45:in `present_resource'
/home/decidim/.rvm/gems/ruby-2.5.3/bundler/gems/decidim-88bdce57dd9a/decidim-core/app/presenters/decidim/log/resource_presenter.rb:31:in `present'
/home/decidim/.rvm/gems/ruby-2.5.3/bundler/gems/decidim-88bdce57dd9a/decidim-core/app/presenters/decidim/log/base_presenter.rb:193:in `i18n_params'
/home/decidim/.rvm/gems/ruby-2.5.3/bundler/gems/decidim-88bdce57dd9a/decidim-core/app/presenters/decidim/log/base_presenter.rb:110:in `block in present_explanation'
actionview (5.2.3) lib/action_view/helpers/capture_helper.rb:41:in `block in capture'
actionview (5.2.3) lib/action_view/helpers/capture_helper.rb:205:in `with_output_buffer'
actionview (5.2.3) lib/action_view/helpers/capture_helper.rb:41:in `capture'
actionview (5.2.3) lib/action_view/helpers/tag_helper.rb:272:in `content_tag'
/home/decidim/.rvm/gems/ruby-2.5.3/bundler/gems/decidim-88bdce57dd9a/decidim-core/app/presenters/decidim/log/base_presenter.rb:107:in `present_explanation'
/home/decidim/.rvm/gems/ruby-2.5.3/bundler/gems/decidim-88bdce57dd9a/decidim-core/app/presenters/decidim/log/base_presenter.rb:121:in `block in present_content'
actionview (5.2.3) lib/action_view/helpers/capture_helper.rb:41:in `block in capture'
actionview (5.2.3) lib/action_view/helpers/capture_helper.rb:205:in `with_output_buffer'
actionview (5.2.3) lib/action_view/helpers/capture_helper.rb:41:in `capture'
actionview (5.2.3) lib/action_view/helpers/tag_helper.rb:272:in `content_tag'
/home/decidim/.rvm/gems/ruby-2.5.3/bundler/gems/decidim-88bdce57dd9a/decidim-core/app/presenters/decidim/log/base_presenter.rb:120:in `present_content'
/home/decidim/.rvm/gems/ruby-2.5.3/bundler/gems/decidim-88bdce57dd9a/decidim-core/app/presenters/decidim/log/base_presenter.rb:154:in `block in present_action_log'
actionview (5.2.3) lib/action_view/helpers/capture_helper.rb:41:in `block in capture'
actionview (5.2.3) lib/action_view/helpers/capture_helper.rb:205:in `with_output_buffer'
actionview (5.2.3) lib/action_view/helpers/capture_helper.rb:41:in `capture'
actionview (5.2.3) lib/action_view/helpers/tag_helper.rb:272:in `content_tag'
/home/decidim/.rvm/gems/ruby-2.5.3/bundler/gems/decidim-88bdce57dd9a/decidim-core/app/presenters/decidim/log/base_presenter.rb:153:in `present_action_log'
/home/decidim/.rvm/gems/ruby-2.5.3/bundler/gems/decidim-88bdce57dd9a/decidim-core/app/presenters/decidim/log/base_presenter.rb:43:in `present'
/home/decidim/.rvm/gems/ruby-2.5.3/bundler/gems/decidim-88bdce57dd9a/decidim-admin/app/helpers/decidim/admin/log_render_helper.rb:17:in `render_log'
/home/decidim/.rvm/gems/ruby-2.5.3/bundler/gems/decidim-88bdce57dd9a/decidim-admin/app/views/decidim/admin/logs/_logs_list.html.erb:11:in `block in 

Additional Context
Related with meta-decidim: https://meta.decidim.org/processes/bug-report/f/210/proposals/14701