pamhyr: Disable posibility to open multiple network window.

src/View/MainWindow.py

@@ -289,11 +289,17 @@ class ApplicationWindow(QMainWindow, ListedSubWindow):
         Returns:
             Nothing
         """
-        if not self.model is None:
+        if (self.model is not None and
+            not self.sub_win_exists("River network")):
             self.network = NetworkWindow(model=self.model, parent=self)
             self.network.show()
 
     def open_geometry(self):
+        """Open geometry window
+
+        Returns:
+            Nothing
+        """
         if not self.model is None:
             geometry = GeometryWindow(parent=self)
             geometry.show()