Fixes errors from PR 5099 (#5102)

Errors were grouped incorrectly.
Fixes #4174

Author: AArdeev

doc/reference/reference_lua/popen.rst

@@ -745,17 +745,22 @@ Below is a list of all ``popen`` functions and handle methods.
         :param handle ph: handle of a child process created with
                           :ref:`popen.new() <popen-new>` or
                           :ref:`popen.shell() <popen-shell>`
-        :param number timeout: since version 3.2.0. The parameter defines the period in seconds for the method to wait for a resolution.
+        :param number timeout: since version 3.2.0. The parameter defines the period in seconds for the method to wait for a resolution. The default value is "infinity".
         :return: (if success) formatted result
+
+                 (if failure) ``nil, err``
         :rtype: res
 
         Possible raised errors:
 
         * ``IllegalParams``: an incorrect handle parameter
         * ``IllegalParams``: called on a closed handle
         * ``FiberIsCancelled``: cancelled by an outside code
+
+        Possible error reasons when ``nil, err`` is returned are:
+        
         * ``TimedOut``: since version 3.2.0. The error means that the method has not reached the positive result but has reached the defined **timeout**.
-        * ``ChannelIsClosed``: since version 3.2.0. The error is returned when the target popen handle is closed from another fiber.
+        * ``ChannelIsClosed``: since version 3.2.0. The error is returned when the target popen handle is closed during the :wait() operation.
 
         The formatted result is a process status table (the same as the
         ``status`` component of the table returned by