Prevent Apdex Alerts from being triggered for periods with no transactions

### Environment SaaS (https://sentry.io/) ### Version _No response_ ### Steps to Reproduce 1. Requires no transactions being accepted by your org, either intentionally or because of depleted quota 2. In the Web UI, go to Alerts -> Create Alert -> Apdex -> Set Conditions 3. On step 1, set the interval to "1 minute interval" for testing purposes 4. On step 3, choose "Static: above or below {x}" and set the "Critical field" to "Below 100" 5. No need to set actions on step 4 6. On step 5, give the rule a name and click "Save Rule" 7. Wait for the 1 minute interval to pass  ### Expected Result Because no transactions are being accepted by Sentry, either intentionally or because of depleted quota, there should be no alert triggered. ### Actual Result Apdex is 0 and therefore an alert is triggered and the alert status is set to "Critical". Alert status remains that way since no transactions are being accepted.