Fix: Handle missing report getting task severity

The task_severity_double function now no longer tries to get the
severity from an undefined report if no report matches the criteria.
Instead it passes the report row id 0 to report_severity, which will
always return SEVERITY_MISSING in this case.

This fixes the check for the "Severity changed" alert condition not
working correctly if the task has no second report for comparison.

src/manage_sql.c

@@ -18861,13 +18861,12 @@ task_severity_double (task_t task, int overrides, int min_qod, int offset)
  || task_target (task) == 0 /* Container task. */)
  return SEVERITY_MISSING;
 
- sql_int64 (&report,
- "SELECT id FROM reports"
- " WHERE reports.task = %llu"
- " AND reports.scan_run_status = %u"
- " ORDER BY reports.creation_time DESC"
- " LIMIT 1 OFFSET %d",
- task, TASK_STATUS_DONE, offset);
+ report = sql_int64_0 ("SELECT id FROM reports"
+ " WHERE reports.task = %llu"
+ " AND reports.scan_run_status = %u"
+ " ORDER BY reports.creation_time DESC"
+ " LIMIT 1 OFFSET %d",
+ task, TASK_STATUS_DONE, offset);
 
  return report_severity (report, overrides, min_qod);
 }
@@ -24694,6 +24693,9 @@ report_severity (report_t report, int overrides, int min_qod)
  double severity;
  iterator_t iterator;
 
+ if (report == 0)
+ return SEVERITY_MISSING;
+
  init_iterator (&iterator,
  "SELECT max(severity)"
  " FROM report_counts"