src/gui_qt/fit/fit_toolbar.py

@@ -51,13 +51,14 @@ class FitToolbar(QtWidgets.QToolBar):
         self.limit_group.triggered.connect(self.change_limit_type)
 
         self.region.sigRegionChanged.connect(self.change_labels)
+        self.change_labels()
 
         self.lineedit.textChanged.connect(self.move_region)
         self.lineedit2.textChanged.connect(self.move_region)
 
     @QtCore.pyqtSlot(QtWidgets.QAction)
     def change_limit_type(self, action: QtWidgets.QAction):
-        is_custom = action.text() == 'Custom'
+        is_custom = (action.text() == 'Custom')
 
         for w in [self.label, self.label2, self.lineedit, self.lineedit2]:
             w.setEnabled(is_custom)
@@ -73,6 +74,24 @@ class FitToolbar(QtWidgets.QToolBar):
         self.lineedit2.blockSignals(False)
 
     def move_region(self):
-        r_min = self.lineedit.text()
+        try:
-        r_max = self.lineedit2.text()
+            r_min = float(self.lineedit.text())
-        self.region.setRegion((float(r_min), float(r_max)), use_log=True)
+        except ValueError:
+            r_min = None
+
+        try:
+            r_max = float(self.lineedit2.text())
+        except ValueError:
+            r_max = None
+
+        if r_min is not None and r_max is not None:
+            self.region.setRegion((r_min, r_max), use_log=True)
+
+    def get_limit(self):
+        action_text = self.limit_group.checkedAction().text()
+
+        return {
+            'None': 'none',
+            'Visible x range': 'x',
+            'Custom': self.region.getRegion(),
+        }[action_text]

src/gui_qt/main/mainwindow.py

@@ -904,17 +904,16 @@ class NMRMainWindow(QtWidgets.QMainWindow, Ui_BaseWindow):
 
     @QtCore.pyqtSlot(QtWidgets.QAction)
     def change_fit_limits(self, action: QtWidgets.QAction):
+        if self.current_graph_widget is None:
+            return
+
         if action == self.action_custom_range and self.fit_dialog.isVisible():
             self.current_graph_widget.add_external(self.fitregion)
         else:
             self.current_graph_widget.remove_external(self.fitregion)
 
     def start_fit(self, parameter, links, fit_options):
-        fit_options['limits'] = {
+        fit_options['limits'] = self.fit_toolbar.get_limit()
-            self.action_no_range: 'none',
-            self.action_x_range: 'x',
-            self.action_custom_range: self.fitregion.getRegion()
-        }[self.ac_group2.checkedAction()]
 
         fit_options['fit_mode'] = {
             self.action_lm_fit: 'lsq',