Only use summary for quote if text is empty

For text messages, summary joins all lines into one, so multi-line quotes
look bad in Thunderbird.

python/tests/test_account.py

@@ -479,7 +479,7 @@ class TestOfflineChat:
     def test_quote(self, chat1):
         """Offline quoting test"""
         msg = Message.new_empty(chat1.account, "text")
-        msg.set_text("message")
+        msg.set_text("Multi\nline\nmessage")
         assert msg.quoted_text is None
 
         # Prepare message to assign it a Message-Id.
@@ -489,7 +489,7 @@ class TestOfflineChat:
         reply_msg = Message.new_empty(chat1.account, "text")
         reply_msg.set_text("reply")
         reply_msg.quote = msg
-        assert reply_msg.quoted_text == "message"
+        assert reply_msg.quoted_text == "Multi\nline\nmessage"
 
     def test_group_chat_many_members_add_remove(self, ac1, lp):
         lp.sec("ac1: creating group chat with 10 other members")

src/message.rs

@@ -764,8 +764,16 @@ impl Message {
             self.param.set(Param::GuaranteeE2ee, "1");
         }
 
-        self.param
+        let text = quote.get_text().unwrap_or_default();
-            .set(Param::Quote, quote.get_summarytext(context, 500).await);
+        self.param.set(
+            Param::Quote,
+            if text.is_empty() {
+                // Use summary, similar to "Image" to avoid sending empty quote.
+                quote.get_summarytext(context, 500).await
+            } else {
+                text
+            },
+        );
 
         Ok(())
     }