Continuity: fix TTFI when EventTiming plugin is missing

[querymetrics]

Fix for https://github.com/akamai/boomerang/issues/331

[github-actions[bot]]

Filename	Size	Change
build/boomerang-1.0.0.min.js	40.4 kB	+30 B (0%)
build/plugins/continuity.min.js	6.58 kB	+5 B (0%)

ℹ️ View Unchanged

| Filename | Size | Change | | |:--- |:---:|:---:|:---:| | `build/plugins/auto-xhr.min.js` | 5.95 kB | 0 B | | | `build/plugins/bw.min.js` | 2.27 kB | 0 B | | | `build/plugins/cache-reload.min.js` | 202 B | 0 B | | | `build/plugins/cache-test-plugin.min.js` | 388 B | 0 B | | | `build/plugins/clicks.min.js` | 705 B | 0 B | | | `build/plugins/compression.min.js` | 846 B | 0 B | | | `build/plugins/consent-inlined-plugin.min.js` | 714 B | 0 B | | | `build/plugins/dns.min.js` | 454 B | 0 B | | | `build/plugins/early.min.js` | 683 B | 0 B | | | `build/plugins/errors.min.js` | 4.84 kB | 0 B | | | `build/plugins/eventtiming.min.js` | 924 B | 0 B | | | `build/plugins/guid.min.js` | 325 B | 0 B | | | `build/plugins/history.min.js` | 1.34 kB | 0 B | | | `build/plugins/iframe-delay.min.js` | 1.03 kB | 0 B | | | `build/plugins/ipv6.min.js` | 714 B | 0 B | | | `build/plugins/memory.min.js` | 1.24 kB | 0 B | | | `build/plugins/mobile.min.js` | 301 B | 0 B | | | `build/plugins/mq.min.js` | 306 B | 0 B | | | `build/plugins/navtiming.min.js` | 1.44 kB | 0 B | | | `build/plugins/painttiming.min.js` | 837 B | 0 B | | | `build/plugins/restiming.min.js` | 5.28 kB | 0 B | | | `build/plugins/rt.min.js` | 4.47 kB | 0 B | | | `build/plugins/spa.min.js` | 1.32 kB | 0 B | | | `build/plugins/third-party-analytics.min.js` | 1.21 kB | 0 B | | | `build/plugins/usertiming.min.js` | 759 B | 0 B | | | `build/plugins/zzz-last-plugin.min.js` | 76 B | 0 B | |

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