better error message for live view on iOS (#121)

ui/src/Live/index.tsx

@@ -2,6 +2,8 @@
 // Copyright (C) 2021 The Moonfire NVR Authors; see AUTHORS and LICENSE.txt.
 // SPDX-License-Identifier: GPL-v3.0-or-later WITH GPL-3.0-linking-exception
 
+import Container from "@material-ui/core/Container";
+import ErrorIcon from "@material-ui/icons/Error";
 import { Camera } from "../types";
 import LiveCamera from "./LiveCamera";
 import Multiview from "./Multiview";
@@ -12,6 +14,21 @@ export interface LiveProps {
 }
 
 const Live = ({ cameras, layoutIndex }: LiveProps) => {
+  if ("MediaSource" in window === false) {
+    return (
+      <Container>
+        <ErrorIcon
+          sx={{
+            float: "left",
+            color: "secondary.main",
+            marginRight: "1em",
+          }}
+        />
+        Live view doesn't work yet on your browser. See{" "}
+        <a href="https://github.com/scottlamb/moonfire-nvr/issues/121">#121</a>.
+      </Container>
+    );
+  }
   return (
     <Multiview
       layoutIndex={layoutIndex}