fix(explore): guard against disposed ECharts instance in release bubbles mouse handlers

[billyvg]

Summary

Fixes JAVASCRIPT-3AP8 — TypeError: Cannot read properties of undefined (reading 'get') in useReleaseBubbles.tsx

Root cause: When a user hovers over a release bubble and then navigates away (or the component unmounts) before the mouseout event fires, the ECharts instance can be disposed while handleMouseOut is still executing. Calling setOption on a disposed ECharts instance triggers an internal crash deep in MarkerModel.mergeOption → GlobalModel.eachSeries, where seriesModel is undefined.

The same disposal race can affect handleMouseOver.

Fix: Add echartsInstance.isDisposed() early-return guards to both handleMouseOver and handleMouseOut. This pattern is already used elsewhere in the codebase (see useChartBoxZoom.tsx:123).

Evidence:

• Sentry issue: https://sentry.sentry.io/issues/JAVASCRIPT-3AP8
• 289 events, 192 users affected
• Seer analysis confirms: "Wrap setOption calls in mouse handlers with a try/catch and add an isDisposed guard to prevent crashes during chart state transitions"
• Crash traceback: useReleaseBubbles.tsx:552 → echartsInstance.setOption → MarkerModel.mergeOption → seriesModel.get(...) where seriesModel is undefined

Test plan

• Manual: Navigate to the /issues/:groupId/events/ page with the release bubbles chart, hover over a bubble, and quickly navigate away — verify no TypeError in the console
• Existing tests for useReleaseBubbles continue to pass

Claude session: https://claude.ai/code/session_01LjN9gb92hUE6jTqQ9dkjAm

Legal Boilerplate

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[github-actions]

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[github-actions]

Backend Test Failures

Failures on 1fe7805 in this run:

tests/sentry/snuba/test_validators.py::SnubaQueryValidatorTest::test_invalid_dataset_sessions_returns_validation_error — log

[gw0] linux -- Python 3.13.1 /home/runner/work/sentry/sentry/.venv/bin/python3
tests/sentry/snuba/test_validators.py:84: in test_invalid_dataset_sessions_returns_validation_error
    assert any("Invalid dataset for alerts" in str(e) for e in non_field_errors)
E   assert False
E    +  where False = any(<generator object SnubaQueryValidatorTest.test_invalid_dataset_sessions_returns_validation_error.<locals>.<genexpr> at 0x7f67c9723a00>)