Fix yield_content error

Author: bradgessler

lib/generators/superform/install/templates/base.rb

@@ -12,7 +12,7 @@ def row(component)
     def around_template(&)
       super do
         error_messages
-        yield
+        yield if block_given?
         submit
       end
     end
@@ -30,4 +30,4 @@ def error_messages
       end
     end
   end
-end
+end