patch 8.2.1959: crash when terminal buffer name is made empty

Problem:    Crash when terminal buffer name is made empty. (Dhiraj Mishra)
Solution:   Fall back to "[No Name]". (closes #7262)
diff --git a/src/buffer.c b/src/buffer.c
index c804348..a4c6a00 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -5648,11 +5648,22 @@
     }
 
     if (buf->b_fname == NULL)
-	return (char_u *)_("[No Name]");
+	return buf_get_fname(buf);
     return NULL;
 }
 
 /*
+ * Get "buf->b_fname", use "[No Name]" if it is NULL.
+ */
+    char_u *
+buf_get_fname(buf_T *buf)
+{
+    if (buf->b_fname == NULL)
+	return (char_u *)_("[No Name]");
+    return buf->b_fname;
+}
+
+/*
  * Set 'buflisted' for curbuf to "on" and trigger autocommands if it changed.
  */
     void