Empty window after minimize and restore

Original Reporter info from Mantis: Alexx2000 @alexx2000

• Reporter name: Alexander Koblov

Description:

I check latest Lazarus 1.6 from fixes branch. I found that when I minimize window in my program and restore it then window is empty, only main menu is visible. I found that this bug was introduced in revision 51115 and was merged in 51152. I can reproduce it only on my big project. I was not able to create a small test case. Tested under Windows 7, 10.

Mantis conversion info:

• Mantis ID: 29445
• Fixed in version: 1.7 (SVN)
• Fixed in revision: 51321 (#251af804),51333 (#0314da0e),51334 (#4c08c761)
• Target version: 1.6