qml: don't auto-pop Scan

TODO: handle cancel by signal too

electrum/gui/qml/components/OpenChannel.qml

@@ -64,6 +64,7 @@ Pane {
                             channelopener.nodeid = page.scanData
                             node.text = channelopener.nodeid
                         }
+                        app.stack.pop()
                     })
                 }
             }

electrum/gui/qml/components/Scan.qml

@@ -24,7 +24,6 @@ Item {
         onFound: {
             scanPage.scanData = scanData
             scanPage.found()
-            app.stack.pop()
         }
     }
 

electrum/gui/qml/components/Send.qml

@@ -84,10 +84,11 @@ Pane {
                     page.onFound.connect(function() {
                         var text = page.scanData
                         if (bitcoin.verify_raw_tx(text)) {
-                            app.stack.push(Qt.resolvedUrl('TxDetails.qml'),
+                            app.stack.replace(Qt.resolvedUrl('TxDetails.qml'),
                                 { rawtx: text }
                             )
                         } else {
+                            app.stack.pop()
                             invoice.recipient = text
                         }
                     })