Reset effect icon transparency when they're hidden (#5877)

CHANGELOG.md

@@ -104,6 +104,7 @@
     Bug #5840: GetSoundPlaying "Health Damage" doesn't play when NPC hits target with shield effect ( vanilla engine behavior )
     Bug #5841: Can't Cast Zero Cost Spells When Magicka is < 0
     Bug #5871: The console appears if you type the Russian letter "Ё" in the name of the enchantment
+    Bug #5877: Effects appearing with empty icon
     Feature #390: 3rd person look "over the shoulder"
     Feature #1536: Show more information about level on menu
     Feature #2386: Distant Statics in the form of Object Paging

apps/openmw/mwgui/spellicons.cpp

@@ -181,7 +181,9 @@ namespace MWGui
             }
             else if (mWidgetMap.find(effectId) != mWidgetMap.end())
             {
-                mWidgetMap[effectId]->setVisible(false);
+                MyGUI::ImageBox* image = mWidgetMap[effectId];
+                image->setVisible(false);
+                image->setAlpha(1.f);
             }
         }