BUG-2644: Fixed a NPRE when exporting to Powerpoint when it's not running yet.

GreenshotOfficePlugin/OfficeExport/PowerpointExporter.cs

@@ -1,19 +1,19 @@
 // Greenshot - a free and open source screenshot tool
 // Copyright (C) 2007-2020 Thomas Braun, Jens Klingen, Robin Krom
-// 
+//
 // For more information see: http://getgreenshot.org/
 // The Greenshot project is hosted on GitHub https://github.com/greenshot/greenshot
-// 
+//
 // This program is free software: you can redistribute it and/or modify
 // it under the terms of the GNU General Public License as published by
 // the Free Software Foundation, either version 1 of the License, or
 // (at your option) any later version.
-// 
+//
 // This program is distributed in the hope that it will be useful,
 // but WITHOUT ANY WARRANTY; without even the implied warranty of
 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 // GNU General Public License for more details.
-// 
+//
 // You should have received a copy of the GNU General Public License
 // along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
@@ -243,7 +243,7 @@ namespace GreenshotOfficePlugin.OfficeExport
                 // Ignore, probably no PowerPoint running
                 return null;
             }
-            if (powerPointApplication.ComObject != null)
+            if (powerPointApplication?.ComObject != null)
             {
                 InitializeVariables(powerPointApplication);
             }