New issue by unspecd on void-packages repository

https://github.com/void-linux/void-packages/issues/29561

Description:
### System

* xuname:  
  *Void 5.10.23_1 x86_64-musl GenuineIntel notuptodate rrrnFFFFFFFFFFF*
* package:  
  ``n/a``

### Expected behavior
```console
$ ./xbps-src -a i686 clean-repocache
```
-- removes obsolete packages from hostdir/repocache-i686

### Actual behavior
```console
$ ls -1 hostdir/repocache-i686/ | wc -
59
$ ./xbps-src -a i686 clean-repocache
Assertion failed: idx < pa->pa_count (portableproplib/prop_array.c: prop_array_remove: 754)
./xbps-src: line 710: 17412 Aborted                 $XBPS_REMOVE_CMD -C /dev/null -c $XBPS_HOSTDIR/repocache-${XBPS_TARGET_ARCH} -O
$ ./xbps-src -a i686 clean-repocache
Removed libunistring-devel-0.9.10_1.i686.xbps from cachedir (obsolete)
Removed readline-devel-8.1.000_1.i686.xbps from cachedir (obsolete)
Removed libltdl-devel-2.4.6_6.i686.xbps from cachedir (obsolete)
Removed less-563_1.i686.xbps from cachedir (obsolete)
Removed ncurses-devel-6.2_4.i686.xbps from cachedir (obsolete)
Removed libpcre-8.44_1.i686.xbps from cachedir (obsolete)
Removed cross-vpkg-dummy-0.37_1.i686.xbps from cachedir (obsolete)
Removed pkg-config-0.29.2_2.i686.xbps from cachedir (obsolete)
Removed libhistory8-8.1.000_1.i686.xbps from cachedir (obsolete)
Removed gc-devel-8.0.4_1.i686.xbps from cachedir (obsolete)
Removed libdb-5.3.28_8.i686.xbps from cachedir (obsolete)
Removed m4-1.4.18_2.i686.xbps from cachedir (obsolete)
Removed base-files-0.141_11.i686.xbps from cachedir (obsolete)
Removed libffi-devel-3.3_2.i686.xbps from cachedir (obsolete)
Removed texinfo-6.7_1.i686.xbps from cachedir (obsolete)
Removed gmp-6.2.1_1.i686.xbps from cachedir (obsolete)
Removed ncurses-libs-6.2_4.i686.xbps from cachedir (obsolete)
Removed libreadline8-8.1.000_1.i686.xbps from cachedir (obsolete)
Removed libffi-3.3_2.i686.xbps from cachedir (obsolete)
Removed libltdl-2.4.6_6.i686.xbps from cachedir (obsolete)
Removed libatomic_ops-7.6.10_1.i686.xbps from cachedir (obsolete)
Removed gmp-devel-6.2.1_1.i686.xbps from cachedir (obsolete)
Removed libunistring-0.9.10_1.i686.xbps from cachedir (obsolete)
Removed automake-1.16.2_2.i686.xbps from cachedir (obsolete)
Removed autoconf-2.69_9.i686.xbps from cachedir (obsolete)
Removed gc-8.0.4_1.i686.xbps from cachedir (obsolete)
Removed libatomic_ops-devel-7.6.10_1.i686.xbps from cachedir (obsolete)
Removed gdbm-1.19_1.i686.xbps from cachedir (obsolete)
Removed perl-5.32.1_2.i686.xbps from cachedir (obsolete)
$ ls -l hostdir/repocache-i686/
total 0
```

### Steps to reproduce the behavior
1. Build 5-10 packages for `i686`.
2. Run `./xbps-src -a i686 clean-repocache`.

The issue is not always reproducible.