Fix context menus on Qt 5.9

app/gui/AppView.qml

@@ -134,7 +134,13 @@ GridView {
             acceptedButtons: Qt.RightButton
             onClicked: {
                 // popup() ensures the menu appears under the mouse cursor
-                appContextMenu.popup()
+                if (appContextMenu.popup) {
+                    appContextMenu.popup()
+                }
+                else {
+                    // Qt 5.9 doesn't have popup()
+                    appContextMenu.open()
+                }
             }
         }
 

app/gui/PcView.qml

@@ -192,7 +192,13 @@ GridView {
             onClicked: {
                 if (!model.addPc) {
                     // popup() ensures the menu appears under the mouse cursor
-                    pcContextMenu.popup()
+                    if (pcContextMenu.popup) {
+                        pcContextMenu.popup()
+                    }
+                    else {
+                        // Qt 5.9 doesn't have popup()
+                        pcContextMenu.open()
+                    }
                 }
             }
         }