When both players have an equal amount of points, which can happen when a non-fractional komi is used, then the game is a draw (jigo). In this case, the impact on the new calculated rating is equally shared.
 
When the rating difference for a game is about zero, your new ratings will not be changed (+0.00 rating diff).
 
However, When your rating difference is greater than zero, for example a 1 dan player plays a 10 kyu player on an even game or with less than 9 stones handicap and normal komi, then there is a difference in rating. Then also the winning propability changes and when the game ends in jigo, the lower ranked player gets an increase in rating while the higher ranked gets a decrease. The difference is just smaller compared to the case, when the lower ranked player would have won.