Fixes #4119 - Bad URLs with hashes are not gracefully handled

Fixes issue #4119
Added regex test to see if hash is valid and if a page with that id
exists, if not load the first page.

js/jquery.mobile.init.js

@@ -77,8 +77,10 @@ define( [ "jquery", "./jquery.mobile.core", "./jquery.mobile.support", "./jquery
 			//remove initial build class (only present on first pageshow)
 			hideRenderingClass();
 
-			// if hashchange listening is disabled or there's no hash deeplink, change to the first page in the DOM
-			if ( !$.mobile.hashListeningEnabled || !$.mobile.path.stripHash( location.hash ) ) {
+			// if hashchange listening is disabled, there's no hash deeplink,
+			// the hash is not valid (contains more than one # or does not start with #)
+			// or there is no page with that hash, change to the first page in the DOM
+			if ( !$.mobile.hashListeningEnabled || /(^#$)|(#.*#.*)|(^[^#].+)/.test( location.hash ) || !$( location.hash + ':jqmData(role="page")' ).length ) {
 				$.mobile.changePage( $.mobile.firstPage, { transition: "none", reverse: true, changeHash: false, fromHashChange: true } );
 			}
 			// otherwise, trigger a hashchange to load a deeplink