optable-targeting: Fix query string construction when IDs are missing.

[justadreamer]

🔧 Type of changes

• bugfix

✨ What's the context?

When there was no input IDs extracted from the incoming request to be sent to Optable Targeting Endpoint - the query string appended to the main endpoint (already containing &t=&o= parameters) would be formed without a leading & essentially leading to query strings like &t=tenant&origin=origingdpr=0 instead of &t=tenant=tenant&origin=origin&gdpr=0 - that lead to Targeting API requests failing with a 404. The test was there, but the test itself was incorrect, thus the bug was not caught :( The code and test are fixed now.

🧠 Rationale behind the change

To eliminate the majority of Targeting API calls resulting in 404s in production

🧪 Test plan

How do you know the changes are safe to ship to production?

• Unit Tests
• Manual Integration Tests

🏎 Quality check

• Are your changes following our code style guidelines? Should be
• Are there any breaking changes in your code? No breaking changes
• Does your test coverage exceed 90%? Should be
• Are there any erroneous console logs, debuggers or leftover code in your changes? None