Added nullish arguments as source type

Author: acezxn

src/tstool/dfbscan_extractor/Javascript/Javascript_NPD_extractor.py

@@ -59,6 +59,7 @@ def extract_sources(self, function: Function) -> List[Value]:
         1. variable = null;
         2. return null;
         3. delete obj.prop;
+        4. func(null);
         """
 
         root_node = function.parse_tree_root_node
@@ -68,6 +69,7 @@ def extract_sources(self, function: Function) -> List[Value]:
         nodes = find_nodes_by_type(root_node, "variable_declarator")
         nodes.extend(find_nodes_by_type(root_node, "assignment_expression"))
         nodes.extend(find_nodes_by_type(root_node, "return_statement"))
+        nodes.extend(find_nodes_by_type(root_node, "arguments"))
 
         sources = []