Component/select: Before uppercasing $child->group, make sure it isn't null

[algernon]

I recently set up Baïkal, and it works wonderfully with most clients I let at it. However, I ran into an issue when I tried using InfCloud pointed at it: my address book didn't display, because Baïkal returned a HTTP 500 to some request InfCloud was making.

I dug into the logs, and I found that the issue is this backtrace:

today at 1:58:13 AM2022/05/11 23:58:13 [error] 23#23: *1387 FastCGI sent in stderr: "PHP message: ErrorException: strtoupper(): Passing null to parameter #1 ($string) of type string is deprecated in /var/www/baikal/vendor/sabre/vobject/lib/Component.php:252
today at 1:58:13 AMStack trace:
today at 1:58:13 AM#0 [internal function]: Baikal\Framework::exception_error_handler()
today at 1:58:13 AM#1 /var/www/baikal/vendor/sabre/vobject/lib/Component.php(252): strtoupper()
today at 1:58:13 AM#2 /var/www/baikal/vendor/sabre/vobject/lib/VCardConverter.php(119): Sabre\VObject\Component->select()
today at 1:58:13 AM#3 /var/www/baikal/vendor/sabre/vobject/lib/VCardConverter.php(55): Sabre\VObject\VCardConverter->convertProperty()
today at 1:58:13 AM#4 /var/www/baikal/vendor/sabre/vobject/lib/Component/VCard.php(189): Sabre\VObject\VCardConverter->convert()
today at 1:58:13 AM#5 /var/www/baikal/vendor/sabre/dav/lib/CardDAV/Plugin.php(829): Sabre\VObject\Component\VCard->convert()
today at 1:58:13 AM#6 /var/www/baikal/vendor/sabre/dav/lib/CardDAV/Plugin.php(244): Sabre\CardDAV\Plugin->convertVCard()
today at 1:58:13 AM#7 /var/www/baikal/vendor/sabre/dav/lib/CardDAV/Plugin.php(189): Sabre\CardDAV\Plugin->addressbookMultiGetReport()

Naturally, I went looking, as this seemed easy to fix, or at least work around. I have no idea what request InfCloud is sending, mind you. I looked at it, it was a lot of XML, I ran away. So I looked at the Baïkal side instead, tracked down the place the error was coming from, and did as this patch does: before calling strtoupper($child->group), I added another check to see if $child->group is non-null.

Now I have my address book shown via InfCloud too, and everything else appears to work as well.

I'm not sure if its the right fix, but it gets the job done, so I figured I'll share.

[codecov]

Codecov Report

Merging #573 (7c50120) into master (06feff3) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

@@             Coverage Diff              @@
##             master     #573      +/-   ##
============================================
- Coverage     98.34%   98.34%   -0.01%     
- Complexity     1884     1885       +1     
============================================
  Files            71       71              
  Lines          4536     4529       -7     
============================================
- Hits           4461     4454       -7     
  Misses           75       75              

Impacted Files	Coverage Δ
lib/Component.php	99.15% <100.00%> (ø)
lib/PHPUnitAssertions.php	91.66% <0.00%> (-0.34%)	⬇️
lib/Parser/Json.php	96.87% <0.00%> (-0.14%)	⬇️
lib/Parser/XML.php	97.45% <0.00%> (-0.05%)	⬇️

📣 Codecov can now indicate which changes are the most critical in Pull Requests. Learn more