catch empty sets before fit

src/gui_qt/main/management.py

@@ -543,7 +543,7 @@ class UpperManagement(QtCore.QObject):
                         else:
                             d = fit_d.Data(_x[inside], _y[inside], we=we[inside], idx=set_id, complex_type=data_complex)
                     except Exception as e:
-                        raise Exception(f'Setting data failed for {set_id}')
+                        raise Exception(f'Setting data failed for {data_i.name}') from e
 
                     d.set_model(m)
                     try:
@@ -559,7 +559,7 @@ class UpperManagement(QtCore.QObject):
             return True
 
         except Exception as e:
-            logger.error('Fit preparation failed', *e.args)
+            logger.error(f'Fit preparation failed with error: {e.args}')
             QtWidgets.QMessageBox.warning(QtWidgets.QWidget(),
                                           'Fit prep failed',
                                           f'Fit preparation failed:\n'

src/nmreval/fit/data.py

@@ -10,6 +10,9 @@ class Data:
     def __init__(self, x, y, we=None, idx=None, complex_type: int = 0):
         self.x = np.asarray(x)
         self.y = np.asarray(y)
+        if self.x.size == 0 or self.y.size == 0:
+            raise ValueError("Data is empty")
+
         if self.y.shape[0] != self.x.shape[0]:
             raise ValueError(f'x and y have different lengths {self.x.shape[0]} and {self.y.shape[0]}')