Rails .each except if - ruby-on-rails

Question

I have a rails table called Movies. Movies are being collected and saved from an API which means that some movies may have a release_date and some may not.
All Movies are being displayed on the home page and they are sorted by {|t| - t.release_date.strftime("%Y%m%d").to_i}
<% #movies.sort_by{|t| - t.release_date.strftime("%Y%m%d").to_i}.each do |movie| %>
<% movie.title %>
<% movie.release_date.strftime("%Y") %>
<% end %>
So this code works fine but only as long as the returned movies have a release date. If they don't have a release date assigned, it gives me the following error.
ActionView::Template::Error (undefined method `strftime' for nil:NilClass):
But im only getting this error if the movie has no release_date.
So how can i add an exception to only display films WITH a release_date, where using strftime would no longer be a problem.
I've tried
<% unless movie.release_date.blank? %>
<% #movies.sort_by{|t| - t.release_date.strftime("%Y%m%d").to_i}.each do |movie| %>
<% #movie.title %>
<% #movie.release_date.strftime("%Y") %>
<% end %>
<% end %>
But that doesn't work as it gives an undefined method for 'movie'

Answer 1

You should be able to use reject to reject nil release_date like follows:
<% #movies.reject{ |m| m.release_date.nil? } %>
Another problem is you are using the variable movie as instance variable #movie within your each block.
Try:
<% #movies.reject{ |m| m.release_date.nil? }.sort_by{|t| - t.release_date.strftime("%Y%m%d").to_i}.each do |movie| %>
<% movie.title %>
<% movie.release_date.strftime("%Y") %>
<% end %>
Update:
And yes, as pointed by #NicolasGarnil in his answer, it's better to do these in SQL side than in ruby side. Select only the required records and let database do the sorting. So you could update your code to be something like:
In controller:
#movies = Movie.where('release_date is not null').order('release_date desc');
Then in your view:
<% #movies.each do |movie| %>
<% movie.title %>
<% movie.release_date.strftime("%Y") %>
<% end %>

Answer 2

For performance reasons you should not be using ruby to sort your records. This should be done at a database level.
You should first ensure that the release_date values are persisted in an appropriate format and then just use Movie.order("release_date desc"). Records with null values will be placed at the end of the results.