Do not show suggestion message when not exist suggestion

**before**

```
$ ./bin/rails g g
Could not find generator 'g'. Maybe you meant nil?
Run `rails generate --help` for more options.
```

**after**

```
$ ./bin/rails g g
Could not find generator 'g'.
Run `rails generate --help` for more options.
```

2 files changed, 5 insertions, 2 deletions

diff --git a/railties/lib/rails/commands/server/server_command.rb b/railties/lib/rails/commands/server/server_command.rb
index 70789e0303..6c4cc3cb86 100644
--- a/railties/lib/rails/commands/server/server_command.rb
+++ b/railties/lib/rails/commands/server/server_command.rb
@@ -302,9 +302,10 @@ module Rails
             MSG
           else
             suggestion = Rails::Command::Spellchecker.suggest(server, from: RACK_SERVERS)
+            suggestion_msg = "Maybe you meant #{suggestion.inspect}?" if suggestion
 
             <<~MSG
-              Could not find server "#{server}". Maybe you meant #{suggestion.inspect}?
+              Could not find server "#{server}". #{suggestion_msg}
               Run `rails server --help` for more options.
             MSG
           end
diff --git a/railties/lib/rails/generators.rb b/railties/lib/rails/generators.rb
index 5e8cebc50a..caf8a33c3c 100644
--- a/railties/lib/rails/generators.rb
+++ b/railties/lib/rails/generators.rb
@@ -272,8 +272,10 @@ module Rails
         else
           options     = sorted_groups.flat_map(&:last)
           suggestion  = Rails::Command::Spellchecker.suggest(namespace.to_s, from: options)
+          suggestion_msg = "Maybe you meant #{suggestion.inspect}?" if suggestion
+
           puts <<~MSG
-            Could not find generator '#{namespace}'. Maybe you meant #{suggestion.inspect}?
+            Could not find generator '#{namespace}'. #{suggestion_msg}
             Run `rails generate --help` for more options.
           MSG
         end