Don't save "display_progress_bar".

src/core/sheet.js

@@ -52,7 +52,7 @@ Abstract character/resume sheet representation.
     function replacer( key,value ) { // Exclude these keys from stringification
       return _.some(['meta', 'warnings', 'computed', 'filt', 'ctrl', 'index',
         'safeStartDate', 'safeEndDate', 'safeDate', 'safeReleaseDate', 'result',
-      'isModified', 'htmlPreview'],
+      'isModified', 'htmlPreview', 'display_progress_bar'],
         function( val ) { return key.trim() === val; }
       ) ? undefined : value;
     }