fix: crop save dropped blue channel brightness/contrast offset (v1.4.2)

m[13] (blue alpha coefficient, always 0) was read as the blue offset instead of
m[14], so saved JPEGs lost the blue brightness/contrast offset and came out with a
color cast. Saturation/rotate were unaffected (no offsets).

Also: version 1.4.2, CHANGELOG entry, dist/ ships imajviewer_1.4.2_amd64.deb
(replaces 1.4.1).

pubspec.yaml

@@ -1,7 +1,7 @@
 name: imajviewer
 description: "Ultra-lightweight image viewer for Linux and Windows."
 publish_to: 'none'
-version: 1.4.1+9
+version: 1.4.2+10
 
 msix_config:
   display_name: ImajViewer