Card - improve error message when reading invalid svg files

Add a test file in samples/images - it's a simple 1x1 pixel white png
saved with a 'svg' extension.

Fix for #228

(cherry picked from commit 32fad2460753a72cc2b0100d0a132512b6eeed81)

# Conflicts:
#	lib/squib/graphics/image.rb

lib/squib/graphics/image.rb

@@ -67,7 +67,12 @@ module Squib
       Squib.logger.warn 'Both an SVG file and SVG data were specified' unless file.to_s.empty? || svg_args.data.to_s.empty?
       return if (file.nil? or file.eql? '') and svg_args.data.nil? # nothing specified TODO Move this out to arg validator
       svg_args.data = File.read(file) if svg_args.data.to_s.empty?
-      svg          = Rsvg::Handle.new_from_data(svg_args.data)
+      begin
+        svg = Rsvg::Handle.new_from_data(svg_args.data)
+      rescue Rsvg::Error::Failed
+        Squib.logger.error "Invalid SVG data. Is '#{file}' a valid svg file?"
+        return
+      end
       box.width    = svg.width  if box.width == :native
       box.height   = svg.height if box.height == :native
       box.width  = svg.width.to_f * box.height.to_f / svg.height.to_f if box.width == :scale

samples/images/_more_load_images.rb

@@ -95,5 +95,8 @@ Squib::Deck.new(width: 825, height: 1125, cards: 1, config: 'load_images_config.
   svg file: 'spanner.svg', width: :deck, height: :deck,
       force_id: true, id: '' # <-- the important part
 
+  # Squib can handle incorrectly formatted svg files
+  svg file: 'bad-svg.svg'
+
   save prefix: 'load_images_', format: :png
 end