Coerce sp_HumanEvents @seconds_sample = 0/NULL to 1 second

@seconds_sample drives the WAITFOR DELAY that paces the XE session. The
duration-math block only populates @waitfor when @seconds_sample > 0,
so passing 0 or NULL left @waitfor at its default of N'' and the
unconditional WAITFOR DELAY @waitfor later crashed with a syntax error.

Tried a RAISERROR/THROW validation first, but the proc body is wrapped
in a TRY/CATCH whose CATCH block tries to ALTER EVENT SESSION ... STOP
on a session that was never created when the failure happens before
session creation. That overrides the original message with a
"session does not exist" error and makes the true problem unguessable.

Coerce to 1 second instead: NULL silently, 0 with a warning pointing
the caller at a more useful value. The proc then completes its normal
create / start / 1-second wait / stop / drop flow and returns empty
result sets. Callers still get a running proc and a discoverable
warning instead of a cryptic crash.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: erikdarlingdata

sp_HumanEvents/sp_HumanEvents.sql

@@ -890,6 +890,25 @@ BEGIN
     RETURN;
 END;
 
+/*
+@seconds_sample drives the WAITFOR DELAY that controls how long the XE session
+samples before we shred results. When NULL it's treated as unset. When
+explicitly 0 the user is asking for no sampling, which would hit the
+unconditional WAITFOR below with an empty @waitfor string and raise a
+syntax error. Coerce NULL and 0 to 1 second — the minimum meaningful
+value — and warn if 0 was explicit.
+*/
+IF @debug = 1 BEGIN RAISERROR(N'Checking seconds_sample parameter', 0, 1) WITH NOWAIT; END;
+IF @seconds_sample IS NULL
+BEGIN
+    SET @seconds_sample = 1;
+END;
+ELSE IF @seconds_sample = 0
+BEGIN
+    RAISERROR(N'@seconds_sample = 0 is not meaningful (nothing would be sampled). Using 1 second instead. Pass a larger value for real sampling.', 0, 1) WITH NOWAIT;
+    SET @seconds_sample = 1;
+END;
+
 
 IF @debug = 1 BEGIN RAISERROR(N'Checking query sort order', 0, 1) WITH NOWAIT; END;
 IF @query_sort_order NOT IN