Fix problems when configure mountpoint:

1. focus on no item and press "Edit" button ,errors occur.
2. configure root mountpoint ok and and just press Enter when the focus
   on no button, errors occur.

	modified:   text/ri_main.py
	modified:   text/ri_newt.py

text/ri_main.py

@@ -54,11 +54,13 @@ while True :
 		elif list[count] == 'information':
 			ri_newt.Prepar_installation()
 		s = ri_newt.Screen.dict[list[count]].set_data()
-
-	if int(s) == 0: 
-		count = count + 1
-	else:
-		count = count - 1 
+        try:
+	    if int(s) == 0: 
+		    count = count + 1
+	    else:
+		    count = count - 1 
+	except:
+            pass
 
 	if count < 0 or count > len(list) - 1:
 		ri_newt.Screen.screen.finish()

text/ri_newt.py

@@ -620,7 +620,10 @@ class MountPoint(Screen):
 			s =  Screen.yesno(self.title, 1, 6, 'TextboxReflowed', 'CListbox', 'eLabel', 'ButtonBar')
 			
 			if s == 0:
-				self.set_mountpoint(Screen.clistbox.current())
+				try:
+				    self.set_mountpoint(Screen.clistbox.current())
+				except:
+				    pass
 				# edit mountpoint
 			elif s == -1:
 				break