Add and apply Style/SafeNavigation rubocop rule

We were already using it most of the time, but not always.

.rubocop_basic.yml

@@ -261,5 +261,8 @@ Style/BlockDelimiters:
 Style/PercentLiteralDelimiters:
   Enabled: true
 
+Style/SafeNavigation:
+  Enabled: true
+
 Style/StringLiterals:
   EnforcedStyle: double_quotes

app/controllers/legislation/draft_versions_controller.rb

@@ -30,7 +30,7 @@ class Legislation::DraftVersionsController < Legislation::BaseController
   private
 
     def visible_draft_versions
-      if current_user && current_user.administrator?
+      if current_user&.administrator?
         @process.draft_versions
       else
         @process.draft_versions.published

app/controllers/legislation/processes_controller.rb

@@ -47,7 +47,7 @@ class Legislation::ProcessesController < Legislation::BaseController
     set_process
     @phase = :debate_phase
 
-    if @process.debate_phase.started? || (current_user && current_user.administrator?)
+    if @process.debate_phase.started? || (current_user&.administrator?)
       render :debate
     else
       render :phase_not_open
@@ -139,7 +139,7 @@ class Legislation::ProcessesController < Legislation::BaseController
       @proposals = @proposals.send(@current_filter).page(params[:page])
     end
 
-    if @process.proposals_phase.started? || (current_user && current_user.administrator?)
+    if @process.proposals_phase.started? || (current_user&.administrator?)
       legislation_proposal_votes(@proposals)
       render :proposals
     else

app/controllers/verification/letter_controller.rb

@@ -51,7 +51,7 @@ class Verification::LetterController < ApplicationController
 
     def login_via_form
       user = User.find_by email: letter_params[:email]
-      if user && user.valid_password?(letter_params[:password])
+      if user&.valid_password?(letter_params[:password])
         sign_in(user)
       end
     end

app/helpers/users_helper.rb

@@ -37,32 +37,32 @@ module UsersHelper
   end
 
   def current_administrator?
-    current_user && current_user.administrator?
+    current_user&.administrator?
   end
 
   def current_moderator?
-    current_user && current_user.moderator?
+    current_user&.moderator?
   end
 
   def current_valuator?
-    current_user && current_user.valuator?
+    current_user&.valuator?
   end
 
   def current_manager?
-    current_user && current_user.manager?
+    current_user&.manager?
   end
 
   def current_poll_officer?
-    current_user && current_user.poll_officer?
+    current_user&.poll_officer?
   end
 
   def current_tracker?
-    current_user && current_user.tracker?
+    current_user&.tracker?
   end
 
   def show_admin_menu?(user = nil)
     current_administrator? || current_moderator? || current_valuator? || current_manager? ||
-      current_tracker? || (user && user.administrator?) || current_poll_officer?
+      current_tracker? || (user&.administrator?) || current_poll_officer?
   end
 
   def interests_title_text(user)

app/models/legislation/people_proposal.rb

@@ -107,7 +107,7 @@ class Legislation::PeopleProposal < ApplicationRecord
   end
 
   def votable_by?(user)
-    user && user.level_two_or_three_verified?
+    user&.level_two_or_three_verified?
   end
 
   def register_vote(user, vote_value)
@@ -145,7 +145,7 @@ class Legislation::PeopleProposal < ApplicationRecord
   protected
 
     def set_responsible_name
-      if author && author.document_number?
+      if author&.document_number?
         self.responsible_name = author.document_number
       end
     end

app/models/legislation/proposal.rb

@@ -108,7 +108,7 @@ class Legislation::Proposal < ApplicationRecord
   end
 
   def votable_by?(user)
-    user && user.level_two_or_three_verified?
+    user&.level_two_or_three_verified?
   end
 
   def register_vote(user, vote_value)
@@ -142,7 +142,7 @@ class Legislation::Proposal < ApplicationRecord
   protected
 
     def set_responsible_name
-      if author && author.document_number?
+      if author&.document_number?
         self.responsible_name = author.document_number
       end
     end

app/models/proposal.rb

@@ -183,7 +183,7 @@ class Proposal < ApplicationRecord
   end
 
   def votable_by?(user)
-    user && user.level_two_or_three_verified?
+    user&.level_two_or_three_verified?
   end
 
   def retired?
@@ -269,7 +269,7 @@ class Proposal < ApplicationRecord
   protected
 
     def set_responsible_name
-      if author && author.document_number?
+      if author&.document_number?
         self.responsible_name = author.document_number
       end
     end

app/models/signature.rb

@@ -37,7 +37,7 @@ class Signature < ApplicationRecord
 
   def assign_signature_to_vote
     vote = Vote.where(votable: signable, voter: user).first
-    vote.update(signature: self) if vote
+    vote&.update(signature: self)
   end
 
   def user_exists?

app/models/user.rb

@@ -172,7 +172,7 @@ class User < ApplicationRecord
   end
 
   def verified_organization?
-    organization && organization.verified?
+    organization&.verified?
   end
 
   def official?