fix: Fixed bug with new panels not always showing initial content

[bmingles]

DH-18347: Fixed bug with new panels not always showing initial content

Testing

from deephaven import time_table

t1 = time_table("PT2S")

t2 = time_table("PT2S")

1. Run the script 1x
2. Close panel for t1
3. Re-run the script
4. Select t2 tab
5. Should see ticking table in t2. Before bug fix, this panel was empty

Regression tests

1. Close all panels
2. Open t1 then t2 from "PANELS" tree view. Both should have ticking tables

[github-actions]

End-to-end Test Summary

Tests 📝	Passed ✅	Failed ❌	Skipped ⏭️	Pending ⏳	Other ❓	Flaky 🍂	Duration ⏱️
6	6	0	0	0	0	0	05:27:02

A ctrf plugin

Detailed Test Results

Name	Status	ms	Flaky 🍂
should default to the correct settings	passed ✅	2127
should return custom settings: Empty configs	passed ✅	213
should return custom settings: Populated configs	passed ✅	148
should be able to load VSCode	passed ✅	1232
should only be visible when a supported file type is active: test.groovy	passed ✅	2941
should only be visible when a supported file type is active: test.py	passed ✅	1309

A ctrf plugin

Failed Test Summary

No failed tests ✨

Flaky Test Summary

No flaky tests detected. ✨