Allow mass-unassigning of issues

Fixes #867

[ci skip]

CHANGELOG

@@ -11,6 +11,7 @@ v 7.9.0 (unreleased)
   - Fix ordering of imported but unchanged projects (Marco Wessel)
   - Mobile UI improvements: make aside content expandable
   - Generalize image upload in drag and drop in markdown to all files (Hannes Rosenögger)
+  - Fix mass-unassignment of issues (Robert Speicher)
 
 v 7.8.1
   - Fix run of custom post receive hooks

app/assets/javascripts/project_users_select.js.coffee

@@ -15,7 +15,7 @@ class @ProjectUsersSelect
               name: 'Unassigned',
               avatar: null,
               username: 'none',
-              id: ''
+              id: -1
             }
 
             data.results.unshift(nullUser)

spec/services/issues/bulk_update_service_spec.rb

@@ -84,6 +84,25 @@ describe Issues::BulkUpdateService do
       expect(@project.issues.first.assignee).to eq(@new_assignee)
     }
 
+    it 'allows mass-unassigning' do
+      @project.issues.first.update_attribute(:assignee, @new_assignee)
+      expect(@project.issues.first.assignee).not_to be_nil
+
+      @params[:update][:assignee_id] = -1
+
+      Issues::BulkUpdateService.new(@project, @user, @params).execute
+      expect(@project.issues.first.assignee).to be_nil
+    end
+
+    it 'does not unassign when assignee_id is not present' do
+      @project.issues.first.update_attribute(:assignee, @new_assignee)
+      expect(@project.issues.first.assignee).not_to be_nil
+
+      @params[:update][:assignee_id] = ''
+
+      Issues::BulkUpdateService.new(@project, @user, @params).execute
+      expect(@project.issues.first.assignee).not_to be_nil
+    end
   end
 
   describe :update_milestone do