Merge pull request #1739 from dart-lang/use_full_hex_values_for_flutter_color_fix

fix empty arg list access
diff --git a/lib/src/rules/use_full_hex_values_for_flutter_colors.dart b/lib/src/rules/use_full_hex_values_for_flutter_colors.dart
index 0292715..fcbc37e 100644
--- a/lib/src/rules/use_full_hex_values_for_flutter_colors.dart
+++ b/lib/src/rules/use_full_hex_values_for_flutter_colors.dart
@@ -55,11 +55,14 @@
     if (node.staticElement?.library?.name == 'dart.ui' &&
         node.staticElement?.returnType?.name == 'Color' &&
         node.staticElement?.name == '') {
-      final argument = node.argumentList.arguments.first;
-      if (argument is IntegerLiteral) {
-        final value = argument.literal.lexeme;
-        if (!value.startsWith('0x') || value.length != 10) {
-          rule.reportLint(argument);
+      final arguments = node.argumentList.arguments;
+      if (arguments.isNotEmpty) {
+        final argument = arguments.first;
+        if (argument is IntegerLiteral) {
+          final value = argument.literal.lexeme;
+          if (!value.startsWith('0x') || value.length != 10) {
+            rule.reportLint(argument);
+          }
         }
       }
     }