SchemaHandler - Add IF EXISTS to dropTable function

[colemanw]

Overview

Prevents errors in the same way dropColumn does by checking that it exists before dropping.

Before

Error if table has already been dropped

After

No error

Comments

This is a tiny piece carved out from #25871

[civibot]

(Standard links)

• If you are reviewing this pull-request, you may wish to consult the test sites and the Review Standards (long template, short template).

[demeritcowboy]

api_v3_SyntaxConformanceTest::testInvalidID_delete with data set #22 ('CustomGroup') TypeError: CRM_Core_BAO_SchemaHandler::dropTable(): Argument #1 ($tableName) must be of type string, null given, called in /home/jenkins/bknix-dfl/build/build-0/web/sites/all/modules/civicrm/CRM/Core/BAO/CustomGroup.php on line 1275

[colemanw]

@demeritcowboy - I fixed it by cleaning up some APIv3 screwyness, or at least making it consistently screwy.