No empty string assignment anymore

Added a condition to the assignment of labels and pathname, so that there won't be an error when aborting the file selection.

mvc/controller.py

@@ -30,14 +30,15 @@ class ControllerClass:
         """
         file_path = askopenfilename(filetypes=((".txt files", "*.txt"),
                                                ("all files", "*.*")))
-        label_text = "File %d: %s" % (fileno, file_path.title().split("/")[-1])
-
-        if fileno == 1:
-            self.model.file_1 = file_path
-            self.view.tf1_label["text"] = label_text
-        else:
-            self.model.file_2 = file_path
-            self.view.tf2_label["text"] = label_text
+        if file_path != "":  # Do not assign an empty file path
+            label_text = "File %d: %s" % (fileno, file_path.title().split("/")[-1])
+
+            if fileno == 1:
+                self.model.file_1 = file_path
+                self.view.tf1_label["text"] = label_text
+            else:
+                self.model.file_2 = file_path
+                self.view.tf2_label["text"] = label_text
 
     def check_for_files(self):
         if self.model.file_1 is None: