Allow last shot to work without an existing source

pyxpad/pyxpad.py

@@ -728,20 +728,20 @@ def lastShot(self):
         """
         Get the latest shot number
         """
-
-        # Find an XPadSource in the list of sources
         from pyxpad.xpadsource import XPadSource
 
-        source = None
-        for _source in self.sources.sources:
-            if isinstance(_source, XPadSource):
-                source = _source
-        if source is None:
-            # None available
-            return
+        try:
+            source = self.sources.sources[0]
+        except IndexError:
+            source = XPadSource()
 
-        # Now ask for the lastshot
-        last_shot_number = source.last_shot_number
+        try:
+            last_shot_number = source.last_shot_number
+        except AttributeError:
+            self.statusbar.showMessage(
+                "Last shot number not available for {source.label}", 1500
+            )
+            return
 
         # Append the shot number to any existing shot numbers
         current_text = self.shotInput.text()

tests/test_pyxpad.py

@@ -29,6 +29,14 @@ def test_get_last_shot(mock_uda, copy_tree_data, pyxpadbot, qtbot):
     assert str(main.shotInput.text()).strip() == MOCK_LAST_SHOT
 
 
+def test_get_last_shot_no_source(mock_uda, pyxpadbot, qtbot):
+    main = pyxpadbot
+
+    main.lastShotButton.setEnabled(True)
+    qtbot.mouseClick(main.lastShotButton, QtCore.Qt.LeftButton)
+    assert str(main.shotInput.text()).strip() == MOCK_LAST_SHOT
+
+
 def test_get_available_signals(mock_uda, pyxpadbot, qtbot):
     main = pyxpadbot