fix(inputs.phpfpm): Check error before continue processing

[PierreF]

Summary

The PHP-FPM input could crash with a nil pointer dereferencing when timeout is used and the connect can't be established (e.g. the PHP-FPM server isn't running).

Checklist

• No AI generated code was used in this PR

Related issues

resolves #15175

[srebhan]

@PierreF sorry I missed this PR and created #15179... :-( I think we should check the errors earlier... Happy to close my PR and take yours, what do you think?

[PierreF]

No problem. I've updated my PR to contains your fix (your commit, with check of errors done earlier) and include my test.

[telegraf-tiger]

Download PR build artifacts for linux_amd64.tar.gz, darwin_arm64.tar.gz, and windows_amd64.zip.
Downloads for additional architectures and packages are available below.

☺️ This pull request doesn't significantly change the Telegraf binary size (less than 1%)

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Artifact URLs

DEB	RPM	TAR GZ	ZIP
amd64.deb	aarch64.rpm	darwin_amd64.tar.gz	windows_amd64.zip
arm64.deb	armel.rpm	darwin_arm64.tar.gz	windows_arm64.zip
armel.deb	armv6hl.rpm	freebsd_amd64.tar.gz	windows_i386.zip
armhf.deb	i386.rpm	freebsd_armv7.tar.gz
i386.deb	ppc64le.rpm	freebsd_i386.tar.gz
mips.deb	riscv64.rpm	linux_amd64.tar.gz
mipsel.deb	s390x.rpm	linux_arm64.tar.gz
ppc64el.deb	x86_64.rpm	linux_armel.tar.gz
riscv64.deb		linux_armhf.tar.gz
s390x.deb		linux_i386.tar.gz
		linux_mips.tar.gz
		linux_mipsel.tar.gz
		linux_ppc64le.tar.gz
		linux_riscv64.tar.gz
		linux_s390x.tar.gz

[srebhan]

Thank you very much for the fix @PierreF!