ERROR o.h.util.JDBCExceptionReporter - Duplicate entry for key 'PRIMARY' - at multiple clicks on Save button

Tested on XE 7.4.2

1. Create a poll and make it Active.
2. Click many quick times on Save button.

Actual result:

• You get for some clicks the status Saved, but for others you get this error message: FAIL: exception Error number 3201 in 3: Exception while saving document qaws:XPoll.
• This is what Java Melody displays:
  WARN o.h.util.JDBCExceptionReporter - SQL Error: 1062, SQLState: 23000
  3/29/16 10:52:35 AM
  /wiki/qaws/get/XPoll/XPollService?xpage=plain&outputSyntax=plain&page=XPoll.TEST+POLL ajax POST ERROR o.h.util.JDBCExceptionReporter - Duplicate entry '9169762205841068148-2-1' for key 'PRIMARY'

Expected result:

• I expect that the app perform only 1st request that should be processed. Even if I click multiple quick times on Save, the app should not let the next requests to be valid until the first one is finished.