When returning an enum value via g_task_return_int, some code assumes
the enum value is always non-negative and thus considers that a negative
value implies an error. This assumption could be invalidated if a
negative value is later added to the enum. To make it less error prone
to future changes, this patch modifies the code to check if the GError
argument to g_task_propagate_error is populated instead.
d308bbf4c6