patch 8.2.4679: cannot have expandcmd() give an error message for mistakes

Problem:    Cannot have expandcmd() give an error message for mistakes.
Solution:   Add an optional argument to give errors. Fix memory leak when
            expanding files fails. (Yegappan Lakshmanan, closes #10071)
diff --git a/src/filepath.c b/src/filepath.c
index 5bf31ea..3786ef6 100644
--- a/src/filepath.c
+++ b/src/filepath.c
@@ -3999,7 +3999,7 @@
 
     // When returning FAIL the array must be freed here.
     if (retval == FAIL)
-	ga_clear(&ga);
+	ga_clear_strings(&ga);
 
     *num_file = ga.ga_len;
     *file = (ga.ga_data != NULL) ? (char_u **)ga.ga_data