check values null

Author: j4qfrost

lib/src/substituter.dart

@@ -55,7 +55,9 @@ class PostgreSQLFormat {
   static String substitute(String fmtString, Map<String, dynamic>? values,
       {SQLReplaceIdentifierFunction? replace}) {
     final converter = PostgresTextEncoder();
-    replace ??= (spec, index) => converter.convert(values?[spec.name]);
+    if (values != null) {
+      replace ??= (spec, index) => converter.convert(values[spec.name]);
+    }
 
     final items = <PostgreSQLFormatToken>[];
     PostgreSQLFormatToken? currentPtr;