Don't bleed through previous themes.

Took 3 minutes

cockatrice/src/interface/theme_manager.cpp

@@ -344,7 +344,17 @@ void ThemeManager::applyStyleAndPalette(const QString &themeName,
         }
 #endif
     } else {
-        base = qApp->palette();
+        // Always start from the style's own standard palette so a previously-applied
+        // theme can never bleed through. qApp->palette() carries the result of the
+        // last theme application and must not be used as a base here — if the current
+        // theme ships no palette file, hasPalette() is false and palCfg.apply() is
+        // skipped, meaning whatever we put in base IS the effective palette.
+        base = style->standardPalette();
+        if (!base.color(QPalette::Window).isValid()) {
+            // Exotic platform style that doesn't implement standardPalette() —
+            // accept the bleed-through risk rather than crash or use garbage.
+            base = qApp->palette();
+        }
     }
 
     // Overlay custom palette colours