patch 8.0.1515: BufWinEnter event fired when opening hidden terminal

Problem:    BufWinEnter event fired when opening hidden terminal.
Solution:   Do not fire BufWinEnter when the terminal is midden and does not
            open a window. (Kenta Sato, closes #2636)
diff --git a/src/terminal.c b/src/terminal.c
index 6b8d353..eca9f1b 100644
--- a/src/terminal.c
+++ b/src/terminal.c
@@ -475,9 +475,12 @@
 	channel_set_nonblock(term->tl_job->jv_channel, PART_IN);
 
 #ifdef FEAT_AUTOCMD
-	++curbuf->b_locked;
-	apply_autocmds(EVENT_BUFWINENTER, NULL, NULL, FALSE, curbuf);
-	--curbuf->b_locked;
+	if (!opt->jo_hidden)
+	{
+	    ++curbuf->b_locked;
+	    apply_autocmds(EVENT_BUFWINENTER, NULL, NULL, FALSE, curbuf);
+	    --curbuf->b_locked;
+	}
 #endif
 
 	if (old_curbuf != NULL)