shadowserver collector: fix reports = '' behaviour

it the parameter is an empty string (or only contains whitespace), behave as if the parameter is not set and select all reports

fixes certtools#2521

intelmq/bots/collectors/shadowserver/collector_reports_api.py

@@ -56,7 +56,9 @@ def init(self):
             raise ValueError('No secret provided.')
 
         if isinstance(self.reports, str):
-            self._report_list = self.reports.split(',')
+            # if reports is an empty string (or only contains whitespace), behave as if the parameter is not set and select all reports
+            reports = self.reports.strip()
+            self._report_list = reports.split(',') if reports else []
         elif isinstance(self.reports, list):
             self._report_list = self.reports
         if isinstance(self.types, str):