Ticket #24873: 28873.4.diff

wp-admin/includes/revision.php

@@ -175 +175 @@
                 }
                 $revisions[ $current_id ]['current'] = true;
         }
-
         // Now, grab the initial diff
         $compare_two_mode = is_numeric( $from );
         if ( ! $compare_two_mode ) {
-                $from = array_keys( array_slice( $revisions, array_search( $selected_revision_id, array_keys( $revisions ) ) - 1, 1, true ) );
-                $from = $from[0];
+                // Check position of selected revision, if at 0 $from should be 0
+                $selected_revision_position = array_search( $selected_revision_id, array_keys( $revisions ) );          
+                if ( 0 !== $selected_revision_position ) 
+                        $from = array_keys( array_slice( $revisions, $selected_revision_position - 1, 1, true ) )[0];
+                else
+                        $from = 0;
         }
 
         $from = absint( $from );

wp-admin/js/revisions.js

@@ -656 +656 @@
                         _(tickCount).times( function( index ){
                                 this.$el.append( '<div style="' + this.direction + ': ' + ( 100 * tickWidth * index ) + '%"></div>' );
                         }, this );
+
+                        this.reportTickPosition();
                 }
         });