Exception and access violation when adding include files and updating includes search path

Original Reporter info from Mantis: Valdas

• Reporter name: Valdas Jankūnas

Description:

How I get that error:

 - prepare INC file;
 - create a New project;
 - in Object Inspector: Add -> Files from file system..;
 - in File dialog choose INC file;
 - "add dir to include search path" dialog appears -> click YES;
 - exception "TCheckListBox Index 0 out of bounds 0 .. -1." pops -> click Abort -> "Access violation" occurs;

 If I choose not to update include files search path then all went without errors.

Additional information:

Attached log of Lazarus (Lazarus compiled with Debug option).
Attached test files.

Mantis conversion info:

• Mantis ID: 34462
• OS: Kubuntu 18.04.1 LTS
• Build: 59352
• Platform: Linux 64 bit
• Version: 2.1 (SVN)
• Fixed in revision: r59357 (#b9e28c2c)