patch 8.2.5041: cannot close a terminal popup with "NONE" job

Problem:    Cannot close a terminal popup with "NONE" job.
Solution:   Adjust the conditions for whether a job is running.
            (closes #10498)
diff --git a/src/undo.c b/src/undo.c
index 7ebad1c..924108c 100644
--- a/src/undo.c
+++ b/src/undo.c
@@ -3574,7 +3574,7 @@
 bufIsChanged(buf_T *buf)
 {
 #ifdef FEAT_TERMINAL
-    if (term_job_running(buf->b_term))
+    if (term_job_running_not_none(buf->b_term))
 	return TRUE;
 #endif
     return bufIsChangedNotTerm(buf);