exporter-collector browser generate console error during sending trace

[jufab]

What version of OpenTelemetry are you using?

0.12.0

What version of Node are you using?

v12.19.0

Please provide the code you used to setup the OpenTelemetry SDK

N/A

What did you do?

Just use the "tracer-web" example

What did you expect to see?

No error in browser console

What did you see instead?

Error during sending trace

Unhandled Promise rejection: Cannot access 'promise' before initialization ; Zone: 20-0.4746337318449656 ; Task: setTimeout ; Value: ReferenceError: Cannot access 'promise' before initialization
    at _onFinish (CollectorExporterBrowserBase.js?d03f:64)
    at _onSuccess (CollectorExporterBrowserBase.js?d03f:57)
    at Object.sendWithBeacon (util.js?7c77:29)
    at eval (CollectorExporterBrowserBase.js?d03f:72)
    at new ZoneAwarePromise (zone.js?d135:913)
    at CollectorTraceExporter.send (CollectorExporterBrowserBase.js?d03f:54)
    at eval (CollectorExporterBase.js?5401:70)
    at new ZoneAwarePromise (zone.js?d135:913)
    at CollectorTraceExporter._export (CollectorExporterBase.js?5401:67)
    at CollectorTraceExporter.export (CollectorExporterBase.js?5401:52) ReferenceError: Cannot access 'promise' before initialization
    at _onFinish (webpack-internal:///./node_modules/@opentelemetry/exporter-collector/build/src/platform/browser/CollectorExporterBrowserBase.js:64:61)
    at _onSuccess (webpack-internal:///./node_modules/@opentelemetry/exporter-collector/build/src/platform/browser/CollectorExporterBrowserBase.js:57:17)
    at Object.sendWithBeacon (webpack-internal:///./node_modules/@opentelemetry/exporter-collector/build/src/platform/browser/util.js:29:9)
    at eval (webpack-internal:///./node_modules/@opentelemetry/exporter-collector/build/src/platform/browser/CollectorExporterBrowserBase.js:72:24)
    at new ZoneAwarePromise (webpack-internal:///./node_modules/zone.js/dist/zone.js:917:33)
    at CollectorTraceExporter.send (webpack-internal:///./node_modules/@opentelemetry/exporter-collector/build/src/platform/browser/CollectorExporterBrowserBase.js:54:25)
    at eval (webpack-internal:///./node_modules/@opentelemetry/exporter-collector/build/src/CollectorExporterBase.js:70:22)
    at new ZoneAwarePromise (webpack-internal:///./node_modules/zone.js/dist/zone.js:917:33)
    at CollectorTraceExporter._export (webpack-internal:///./node_modules/@opentelemetry/exporter-collector/build/src/CollectorExporterBase.js:67:16)
    at CollectorTraceExporter.export (webpack-internal:///./node_modules/@opentelemetry/exporter-collector/build/src/CollectorExporterBase.js:52:14)

[jufab]

I think i have an idea for the bugfix : i prepare a PR