Fix crashes when localStorage not available

As reported by @bimlas in https://github.com/Jermolene/TiddlyWiki5/issues/3945#issuecomment-496797809

plugins/tiddlywiki/browser-storage/rawmarkup.js

@@ -27,6 +27,12 @@ if(Object.prototype.hasOwnProperty.call($tw.hooks.names,hookName)) {
 function hookBootTiddlersLoaded() {
 	var url = window.location.pathname,
 		log = [];
+	// Check that browser storage is available
+	try {
+		window.localStorage;
+	} catch(e) {
+		return;
+	}
 	// Step through each browsder storage item
 	for(var index=0; index<window.localStorage.length; index++) {
 		var key = window.localStorage.key(index),

plugins/tiddlywiki/dynaview/dynaview.js

@@ -181,15 +181,12 @@ function saveScrollPosition() {
 }
 
 function restoreScrollPosition() {
-	var str = window.localStorage.getItem(LOCAL_STORAGE_KEY_PREFIX + window.location.pathname),
-		json;
-	if(str) {
-		try {
-			json = JSON.parse(str);
-		} catch(e) {
-			// Ignore errors
-		};
-	}
+	var json;
+	try {
+		json = JSON.parse(window.localStorage.getItem(LOCAL_STORAGE_KEY_PREFIX + window.location.pathname));
+	} catch(e) {
+		// Ignore errors
+	};
 	return json;
 }