google.charts.load('current', {packages: ['corechart']});
To
google.charts.load('45', {packages: ['corechart']});
The first argument to google.charts.load is the version name or number, as a string. If you specify 'current', this causes the latest official release of Google Charts to be loaded. If you want to try the candidate for the next release, use 'upcoming' instead. In general there will be very little difference between the two, and they'll be completely identical except when a new release is underway.