TAChart: Improve bar effects in TABGRAUtils. Based on patch by "circular"

git-svn-id: http://svn.freepascal.org/svn/lazarus/trunk@40212 4005530d-fff6-0310-9dd1-cebe43e6787f
TAChart: Fix access violation while deleting an active TChartGUIConnector

git-svn-id: http://svn.freepascal.org/svn/lazarus/trunk@40213 4005530d-fff6-0310-9dd1-cebe43e6787f