Make default value a str (#3931)

Author: kddejong

src/cfnlint/rules/parameters/Default.py

@@ -140,7 +140,7 @@ def match(self, cfn: Template) -> RuleMatches:
             default_value = paramvalue.get("Default")
             if default_value is not None and self.is_list(paramvalue):
                 comma_delimited_default_values = [
-                    x.strip() for x in default_value.split(",")
+                    x.strip() for x in str(default_value).split(",")
                 ]
                 for value in comma_delimited_default_values:
                     param_cdl_matches.extend(

test/fixtures/templates/good/parameters/default.yaml

@@ -75,5 +75,7 @@ Parameters:
       - three,four
   CDLWithoutDefault:
     Type: CommaDelimitedList
-
+  StringList:
+    Type: List<String>
+    Default: False
 Resources: {}