Do not assign floating references to autoptrs

[swick]

Operating System

XDG Desktop Portal version

1.18

XDG Desktop Portal version (Other)

No response

Desktop Environment

Other

Desktop Environment (Other)

No response

Expected Behavior

Correct use of g_autoptr and floating refs

Current Behavior

We have a bunch of cases where we assign the result of g_variant_builder_end to a GVariant autoptr which will unref the floating variant in an early exit which is an error because the reference returned is floating:

g_autoptr(GVariant) options = NULL;
...
options = g_variant_builder_end (&options_builder);
if (...)
  return;

Steps to Reproduce

.

Anything else we should know?

No response