moveit_ros_control_interface: Fix dangling reference

[JafarAbdi]

Description

Checklist

• Required by CI: Code is auto formatted using clang-format
• Extend the tutorials / documentation reference
• Document API changes relevant to the user in the MIGRATION.md notes
• Create tests, which fail without this PR reference
• Include a screenshot if changing a GUI
• While waiting for someone to review your request, please help review another open pull request to support the maintainers

[codecov]

Codecov Report

Merging #710 (069ed67) into main (1843da4) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #710   +/-   ##
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  Coverage   54.18%   54.18%           
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  Files         192      192           
  Lines       20186    20186           
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  Hits        10935    10935           
  Misses       9251     9251           

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[henningkayser]

Are you sure this is a dangling reference? From the code I don't see why this would happen (result_future doesn't go out of scope here). Not knowing your issue, I'd suspect that we are getting an invalid future while the code only checks for timeout.
Side note: is async_send_request() guaranteed to return a valid future?

[JafarAbdi]

Are you sure this is a dangling reference? From the code I don't see why this would happen (result_future doesn't go out of scope here). Not knowing your issue, I'd suspect that we are getting an invalid future while the code only checks for timeout.

Yes, I'm pretty sure, see P2012R1 for why this's happening

[henningkayser]

Are you sure this is a dangling reference? From the code I don't see why this would happen (result_future doesn't go out of scope here). Not knowing your issue, I'd suspect that we are getting an invalid future while the code only checks for timeout.

Yes, I'm pretty sure, see P2012R1 for why this's happening

I see, so get() returned a temporary copy instead of a reference so that the message ends up being a dangling reference...

I think it might still make sense to check for valid() in general, but that doesn't need to be part of this fix.