Handle bad gateway error when starting direct chat

CHANGELOG.md

@@ -56,8 +56,8 @@ and this project adheres to
 - Fix the error message shown when trying to start a direct chat with or 
   invite a non-existing user
 
-- Handle Matrix 502 errors returned when trying to invite a user with an
-  incorrect or unresponsive server in their ID
+- Handle Matrix 502 errors returned when trying to start a direct chat or 
+  invite a user with an incorrect or unresponsive server in their ID
 
 - Correctly hide `socket.gaierror` error popups that appear when the
   internet connection drops

src/gui/Pages/AddChat/DirectChat.qml

@@ -47,6 +47,12 @@ HBox {
                 if (type === "MatrixNotFound")
                     txt = qsTr("This user does not exist")
 
+                if (type === "MatrixBadGateway")
+                    txt = qsTr(
+                        "Server error while trying to find user, please " +
+                        "verify the entered user ID"
+                    )
+
                 errorMessage.text = txt
             })
         },