added qerror() in set_selected_action

Author: Halavus

changelog.txt

@@ -31,6 +31,7 @@ Template for new versions:
 ## New Features
 
 ## Fixes
+- `gui/siegemanager`: Added error message in the console if no siege engine is selected
 
 ## Misc Improvements
 

gui/siegemanager.lua

@@ -416,6 +416,10 @@ end
 function SiegeEngineList:set_selected_action(action)
     local _, selected = self.subviews.list:getSelected()
 
+    if not selected then
+        qerror('No siege engine selected')
+    end
+    
     local successful = set_siege_engine_action({selected.data}, action)
     if not successful then
         self:refresh_view(true)