fix: backport shared default docker icon fix to 7.3

[Eli Bosley (elibosley)]

Summary

Backport of #2693 (chodeus (@chodeus), fixes #2691) into the 7.3 release branch for the 7.3.3 patch release. Clean cherry-pick, no conflicts — 7.3 and master were identical at these two files.

Docker manager records the shared fallback icon /plugins/dynamix.docker.manager/images/question.png for icon-less containers, then removeContainer() unlinks it whenever such a container is removed or updated (e.g. via CA Docker Auto-Update). Once the file is gone, every icon-less container's onerror fallback re-requests it in a tight loop until the next reboot — this is what's generating the nginx log spam reported in the forums and increasingly on Discord.

Changes

Identical to #2693:

• DockerClient.php (removeContainer()) — skip the icon unlink when the recorded icon is the shared default. Per-container cached icons (<name>-icon.png) are still cleaned up as before.
• DockerContainers.php — quote the onerror attribute and guard it with this.onerror=null, so a missing fallback costs one failed request per image instead of an endless 404 retry loop.

Testing

• php -l clean on both changed files.
• Cherry-picked cleanly from master (6f28eb6) with no conflicts; diff is byte-identical to the original PR.
• Original PR fix: don't delete the shared default docker icon when removing an icon-less container #2693 already has an independent QA pass recorded (functional validation on 7.3.2 + plugin-based install/rollback validation) — see linked Linear ticket.

Related to OS-628

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🔧 PR Test Plugin Available

A test plugin has been generated for this PR that includes the modified files.

Version: 2026.07.29.2242
Build: View Workflow Run

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📝 Modified Files:

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emhttp/plugins/dynamix.docker.manager/include/DockerClient.php
emhttp/plugins/dynamix.docker.manager/include/DockerContainers.php

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