patch 8.2.5107: some callers of rettv_list_alloc() check for not OK

Problem:    Some callers of rettv_list_alloc() check for not OK. (Christ van
            Willegen)
Solution:   Use "==" instead of "!=" when checking the return value.
diff --git a/src/mouse.c b/src/mouse.c
index a66c00d..2297f81 100644
--- a/src/mouse.c
+++ b/src/mouse.c
@@ -3099,7 +3099,7 @@
     linenr_T	lnum = 0;
     varnumber_T column = 0;
 
-    if (rettv_dict_alloc(rettv) != OK)
+    if (rettv_dict_alloc(rettv) == FAIL)
 	return;
     d = rettv->vval.v_dict;