Allow deleting all files for multiple file upload. Fixes #1990

lib/carrierwave/mounter.rb

@@ -41,7 +41,7 @@ def uploaders
     end
 
     def cache(new_files)
-      return if new_files.blank?
+      return if !new_files.is_a?(Array) && new_files.blank?
       old_uploaders = uploaders
       @uploaders = new_files.map do |new_file|
         handle_error do

spec/mount_multiple_spec.rb

@@ -309,6 +309,16 @@ def monkey
           expect { instance.store_images! }.not_to raise_error
           expect(instance.images.map(&:identifier)).to be_empty
         end
+
+        it "allows deleting all files" do
+          instance.images = []
+          expect(instance.images.map(&:identifier)).to be_empty
+        end
+
+        it "allows assignment of uploader instances" do
+          instance.images = [instance.images[0]]
+          expect(instance.images.map(&:identifier)).to eq ['bork.txt']
+        end
       end
     end