Fix error backtrace debug logging && Do not log request dump if it is not parsed (#2376)

lib/puma/error_logger.rb

@@ -51,8 +51,8 @@ module Puma
 
       string_block = []
       string_block << title(options)
-      string_block << request_dump(req) if req
-      string_block << error_backtrace(options) if error
+      string_block << request_dump(req) if request_parsed?(req)
+      string_block << error.backtrace if error
 
       ioerr.puts string_block.join("\n")
     end

test/test_error_logger.rb

@@ -59,6 +59,23 @@ class TestErrorLogger < Minitest::Test
     end
   end
 
+  def test_debug_backtrace_logging
+    with_debug_mode do
+      def dummy_error
+        raise StandardError.new('non-blank')
+      rescue => e
+        Puma::ErrorLogger.stdio.debug(error: e)
+      end
+
+      _, err = capture_io do
+        dummy_error
+      end
+
+      assert_match %r!non-blank!, err
+      assert_match %r!:in `dummy_error'!, err
+    end
+  end
+
   private
 
   def with_debug_mode