Did you mean ZP_OpenStreetmap in github?
No, as you can read there it is abandoned becuase it is incorporated in Zenphoto.
I am referring to the master build (also known as support build) of Zenphoto from GitHub. Linked from the download page and also mentioned on the installation page: https://www.zenphoto.org/news/installation-and-upgrading/
Just tested again. Image with good GPS info returned no errors in apache error log or debug log.
Image with bad GPS info returns this: (debug)
{1406444:Tue, 09 Mar 2021 16:28:44 GMT}
NOTICE: Trying to access array offset on value of type null in /var/www/cms.waltrips.com/zp-core/zp-extensions/openstreetmap.php on line 772
openStreetMap->printMap called from printOpenStreetMap >>.>(openstreetmap.php [1056])
from include (image.php [85])
from include (index.php [130])
from index.php [56]
{1406444:Tue, 09 Mar 2021 16:28:44 GMT}
NOTICE: Trying to access array offset on value of type null in /var/www/cms.waltrips.com/zp-core/zp-extensions/openstreetmap.php on line 772
openStreetMap->printMap called from printOpenStreetMap (openstreetmap.php [1056])
from include (image.php [85])
from include (index.php [130])
(apache)
[Tue Mar 09 11:28:44.118590 2021] [php7:notice] [pid 1406444] [client 192.168.1.104:54173] PHP Notice: Trying to access array offset on value of type null in /var/www/cms.waltrips.com/zp-core/zp-extensions/openstreetmap.php on line 772, referer: http://cms.waltrips.com/index.php?album=Hocking-Hills/10-26-20%20Old%20Man%27s%20Cave%20%26%20Rock%20House&image=20201026_124914.jpg
[Tue Mar 09 11:28:44.118775 2021] [php7:notice] [pid 1406444] [client 192.168.1.104:54173] PHP Notice: Trying to access array offset on value of type null in /var/www/cms.waltrips.com/zp-core/zp-extensions/openstreetmap.php on line 772, referer: http://cms.waltrips.com/index.php?album=Hocking-Hills/10-26-20%20Old%20Man%27s%20Cave%20%26%20Rock%20House&image=20201026_124914.jpg
Looking at the code, and I think you already said, something bad is being passed. the error does not point to what that is directly
I will DL 1.5.7 and 1.5.8 and try them from git (Install is currently from GIT
Fretzl provided a direct link above and it is linkeed on our download page. Otherwise the green button on https://github.com/zenphoto/zenphoto
I am seeing new error... but it is not tied to web access
{3920463:Tue, 09 Mar 2021 20:49:45 GMT}
NOTICE: Uninitialized string offset: 1 in /var/www/cms.waltrips.com/zp-core/exif/makers/gps.php on line 82
formatGPSData called from parseGPS (gps.php [216])
from read_entry (exif.php [830])
from read_exif_data_raw (exif.php [1036])
from read_exif_data_protected (functions.php [2451])
from Image->updateMetaData (class-image.php [340])
from Gallery->garbageCollect (class-gallery.php [818])
from admin-refresh-metadata.php [33]
It seems that your image has invalid or corrupt meta data as the notice above tells. That is the core metadata handler and not the OSM plugin.
For example if there a values but not "real coordinates". Currently there is no check if the coordinates are valid itself. I have to look at the exif handler what it exaclty does and if there is already a check (it is technically a 3rd party tool that was taken in once).
I looked at the exif library and since it is a bit old it and I am not that familiar with it in detail, it seems not to use the PHP standard function exif_read_data() for reading the data but instead directly parses the file on its own.
I guess this library was made before this function was available. Perhaps not the best way to parse exif data anymore. And ZP does use exif_read_data() for getting image rotation values for example.