Issues reported as "Unknown OS"

[vaind]

Looks like iOS/macOS issues are missing the OS info. Examples:

• https://sentry.io/organizations/sentry-sdks/issues/3410159820/?project=5428562&query=is%3Aunresolved
• https://stackoverflow.com/questions/72853304/sentry-doesnt-provide-operating-system-on-events

[bruno-garcia]

Thanks for raising Ivan. We need to look into this.

[marandaneto]

The issue is that we have to merge all the context items instead of adding them only if it does not exist:

sentry-dart/flutter/lib/src/default_integrations.dart

Lines 190 to 192 in bdc6e0f

	} else if (eventContexts[key] == null) {
	eventContexts[key] = value;
	}

[ueman]

See also #766