[Bug 50064] New: A transparent Agent.exe window is shown when Battle.Net launches

[WineHQ Bugzilla]

https://bugs.winehq.org/show_bug.cgi?id=50064

Bug ID: 50064
           Summary: A transparent Agent.exe window is shown when
                    Battle.Net launches
           Product: Wine-staging
           Version: 5.20
          Hardware: x86-64
                OS: Linux
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: -unknown
          Assignee: [e-mail]
          Reporter: [e-mail]
                CC: [e-mail], [e-mail]
   Regression SHA1: 3cea972271b4529e332c75b06f902c80e7de1798
      Distribution: ArchLinux

Since 3cea972271b4529e332c75b06f902c80e7de1798 (Rebase against
f4a66ad257df4605e73dfea792eec55a70a04e84) and with all later staging commits,
including 5.20 release, when you launch Battle.Net (a client for Blizzard
games), a transparent Agent.exe is shown. 
Normally, there shouldn't be any window shown for Agent.exe at all.
With staging commit b49e8743866224df57eb1032b6c63c999b28c808 and older, the
issue cannot be reproduced.
Mainline wine (5.20) doesn't have this issue, and
8d04884c1f6aa6b21435130e42978fdeac06df55 (Updated
winex11.drv-Query_server_position patchset …), which was supposed to fix this,
had no effect. More than that, using a build with that patchset disabled did
not get rid of the issue.