fix: telemetry init channel unsuccessful leads to panic

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What's changed and what's your intention?

following #20000

bug report in Slack: https://risingwave-community.slack.com/archives/C03BW71523T/p1736509111698569
and provided log file: https://risingwave-community.slack.com/files/U05J27L4A9L/F088411E1D1/rw.logs

see from the log that a line is rw-standalone-compute risingwave_common::telemetry::report: Telemetry failed to set event reporting tx, event reporting will be disabled.

I am not sure why it cannot allocate a channel and has not been reproduced yet. Proposing adding a check before handling events related info

update: shared static var leads to the issue in standalone mode. the details described in the comments.

Checklist

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Release note

[hzxa21]

Rest LGTM