Do not show Timetable till subjects are not added.

components/Timetable.js

@@ -2,6 +2,7 @@ import React from "react";
 import PropTypes from "prop-types";
 import {
 	Portal,
+	Text,
 } from "react-native-paper";
 import { createStackNavigator } from "@react-navigation/stack";
 
@@ -12,6 +13,17 @@ const Stack = createStackNavigator();
 
 export default function Timetable({ addTimetableEntry, removeTimetableEntry, timetable, subjects }) {
 	const days = ["Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"];
+	if (subjects.length === 0) {
+		return (
+			<Text
+				style={{
+					textAlign: "center",
+					marginTop: 12,
+				}}
+			>
+				No Subjects added. Add Subjects first.
+			</Text>);
+	}
 	return (
 		<Portal.Host><Stack.Navigator headerMode="none">
 			<Stack.Screen name="Timetable">

components/timetable/AddEntry.js

@@ -47,19 +47,22 @@ function AddEntry({addTimetableEntry, days, day, subjects, navigation }) {
 	}
 
 	function submit() {
-		if (subject.id === null) {
-			setSnackbar({ visible: true, message: "Missing subject." });
-			return;
-		} else if (start === null) {
-			setSnackbar({ visible: true, message: "Missing start time." });
-			return;
-		} else if (end === null) {
-			setSnackbar({ visible: true, message: "Missing end time." });
-			return;
-		} else if (count === 0) {
-			setSnackbar({ visible: true, message: "Missing count." });
+		let message = "";
+		if (subject.id === null)
+			message = "Missing Subject";
+		else if (start === null)
+			message =  "Missing start time.";
+		else if (end === null)
+			message =  "Missing end time.";
+		else if (count === 0)
+			message =  "Missing count.";
+
+		if (message !== "") {
+			setSnackbar({visible: true, message: message});
+			setTimeout(() => setSnackbar({ visible: false, message: null }), 2000);
 			return;
 		}
+
 		addTimetableEntry(day, {
 			sub_id: subject.id,
 			count,