Fix unable to uncheck the mount read only check box

Change-Id: I1bbc25df6f35f79549f1eb06feb4db9ec0475aa5
diff --git a/gui/action.cpp b/gui/action.cpp
index fbd80dc..97d95f1 100644
--- a/gui/action.cpp
+++ b/gui/action.cpp
@@ -1798,7 +1798,7 @@
 	} else {
 		TWPartition* Part = PartitionManager.Find_Partition_By_Path("/system");
 		if (Part) {
-			if (DataManager::GetIntValue("tw_mount_system_ro")) {
+			if (arg == "0") {
 				DataManager::SetValue("tw_mount_system_ro", 0);
 				Part->Change_Mount_Read_Only(false);
 			} else {