patch 8.2.2908: crash when using a terminal popup window from cmdline window

Problem:    Crash when using a terminal popup window from the cmdline window.
Solution:   Instead of checking cmdwin_type call cmdwin_is_active().
            (closes #8286)
diff --git a/src/terminal.c b/src/terminal.c
index 9ff498f..2189d01 100644
--- a/src/terminal.c
+++ b/src/terminal.c
@@ -445,6 +445,13 @@
 
     if (check_restricted() || check_secure())
 	return NULL;
+#ifdef FEAT_CMDWIN
+    if (cmdwin_type != 0)
+    {
+	emsg(_(e_cannot_open_terminal_from_command_line_window));
+	return NULL;
+    }
+#endif
 
     if ((opt->jo_set & (JO_IN_IO + JO_OUT_IO + JO_ERR_IO))
 					 == (JO_IN_IO + JO_OUT_IO + JO_ERR_IO)