windows: Fix crash in for Windows versions < 17763

In Windows versions < 17763, `GetProcAddress("#132")` from `uxtheme.dll`
also returns a non-null pointer. However, the function does not match
the expected `extern "system" fn() -> bool` prototype, which causes a
crash when it is called.

This fix ensures compatibility by adding proper checks to prevent such
crashes on older Windows versions.

src/changelog/unreleased.md

@@ -39,3 +39,7 @@ The migration guide could reference other migration examples in the current
 changelog entry.
 
 ## Unreleased
+
+### Fixed
+
+- On Windows, fixed crash in should_apps_use_dark_mode() for Windows versions < 17763.

src/platform_impl/windows/dark_mode.rs

@@ -132,7 +132,13 @@ fn should_apps_use_dark_mode() -> bool {
     static SHOULD_APPS_USE_DARK_MODE: Lazy<Option<ShouldAppsUseDarkMode>> = Lazy::new(|| unsafe {
         const UXTHEME_SHOULDAPPSUSEDARKMODE_ORDINAL: PCSTR = 132 as PCSTR;
 
-        let module = LoadLibraryA("uxtheme.dll\0".as_ptr());
+        // We won't try to do anything for windows versions < 17763
+        // (Windows 10 October 2018 update)
+        if !*DARK_MODE_SUPPORTED {
+            return None;
+        }
+
+        let module = LoadLibraryA("uxtheme.dll\0".as_ptr().cast());
 
         if module == 0 {
             return None;