Changed not to raise error for wrong filter type

lib/pnglitch/errors.rb

@@ -33,11 +33,4 @@ def initialize filename
       super m
     end
   end
-
-  class FilterTypeError < TypeError
-    def initialize filter_type, scanline_no
-      m = filter_type.to_s + ' is not a valid filter type, at scanline no ' + scanline_no.to_s + '.'
-      super m
-    end
-  end
 end

lib/pnglitch/scanline.rb

@@ -124,8 +124,10 @@ def register_filter_decoder decoder = nil, &block
     def save
       pos = @io.pos
       @io.pos = @start_at
-      filter = Filter.guess(@filter_type)
-      raise FilterTypeError.new(@filter_type, @index) if filter.nil?
+      filter = Filter.guess @filter_type
+      if filter.nil?
+        filter = @filter_type.to_i
+      end
       @io << [filter].pack('C')
       @io << self.data.slice(0, @data_size).ljust(@data_size, "\0")
       @io.pos = pos

spec/pnglitch_spec.rb

@@ -561,24 +561,6 @@
           end
         }.not_to raise_error
       end
-
-      it 'should raise an error when it drops the filters' do
-        expect {
-          PNGlitch.open infile do |png|
-            png.filtered_data.pos = png.filtered_data.size / png.height * 96.3
-            chunk = png.filtered_data.read
-            png.filtered_data.rewind
-            10.times do
-              png.filtered_data << chunk
-            end
-            png.each_scanline do |line|
-              line.gsub! /\d/, 'x'
-              line.filter_type = rand(4)
-            end
-            png.output outfile
-          end
-        }.to raise_error PNGlitch::FilterTypeError
-      end
     end
 
     context 'when re-filtering with same filters' do