style: if ! changed by unless

- if ! changed by unless as it is more readable
- !object.blank? is equivalent to object.present?, also more readable

app/views/admin/events/_proposal.html.haml

@@ -106,13 +106,13 @@
           %td
             = @event.language
 
-      - if !@event.room.nil?
+      - unless @event.room.nil?
         %tr
           %td
             %b Room
           %td
             = @event.room.name
-      - if !@event.start_time.nil?
+      - unless @event.start_time.nil?
         %tr
           %td
             %b Scheduled time

app/views/admin/events/index.html.haml

@@ -62,7 +62,7 @@
               - bgcolor=""
             %td{:style=>"background-color: #{bgcolor}"}
               - if @program.show_voting?
-                - if !event.submitter.nil?
+                - unless event.submitter.nil?
                   =link_to event.submitter.name, admin_user_path(event.submitter)
                   - if event.submitter.registrations.count < 1
                     (Unregistered!)

app/views/admin/events/show.html.haml

@@ -23,7 +23,7 @@
           - @event.versions.each do |version|
             %tr
               %td
-                - if !version.whodunnit.nil?
+                - unless version.whodunnit.nil?
                   = User.find(version.whodunnit).name
                 - else
                   No user (probably via the console)
@@ -35,4 +35,3 @@
                 - version.changeset.each_key do |key|
                   = "#{key}: #{version.changeset[key][0]} -> #{version.changeset[key][1]}"
                   %br
-

app/views/admin/lodgings/index.html.haml

@@ -10,7 +10,7 @@
     - slice.each do |lodging|
       .col-md-4
         .thumbnail
-          - if !lodging.picture?
+          - unless lodging.picture?
             %p.text-center
               %i.fa.fa-home.fa-5x
           - else