Fix memory management for tray icon title and tooltip

Replaces previous pointer allocation and freeing logic with correct usage of ffi.malloc.free for title and tooltip setters. Ensures proper memory deallocation and prevents potential memory leaks when setting tray icon properties.

Author: lijy91

packages/nativeapi/lib/src/tray_icon.dart

@@ -165,11 +165,19 @@ class TrayIcon
   }
 
   set title(String? title) {
-    final titlePtr = title != null
-        ? title.toNativeUtf8().cast<Char>()
-        : nullptr;
-    bindings.native_tray_icon_set_title(_nativeHandle, titlePtr);
-    bindings.free_c_str(titlePtr);
+    if (title != null) {
+      final titleUtf8 = title.toNativeUtf8();
+      try {
+        bindings.native_tray_icon_set_title(
+          _nativeHandle,
+          titleUtf8.cast<Char>(),
+        );
+      } finally {
+        ffi.malloc.free(titleUtf8);
+      }
+    } else {
+      bindings.native_tray_icon_set_title(_nativeHandle, nullptr);
+    }
   }
 
   String? get tooltip {
@@ -180,11 +188,19 @@ class TrayIcon
   }
 
   set tooltip(String? tooltip) {
-    final tooltipPtr = tooltip != null
-        ? tooltip.toNativeUtf8().cast<Char>()
-        : nullptr;
-    bindings.native_tray_icon_set_tooltip(_nativeHandle, tooltipPtr);
-    ffi.calloc.free(tooltipPtr);
+    if (tooltip != null) {
+      final tooltipUtf8 = tooltip.toNativeUtf8();
+      try {
+        bindings.native_tray_icon_set_tooltip(
+          _nativeHandle,
+          tooltipUtf8.cast<Char>(),
+        );
+      } finally {
+        ffi.malloc.free(tooltipUtf8);
+      }
+    } else {
+      bindings.native_tray_icon_set_tooltip(_nativeHandle, nullptr);
+    }
   }
 
   Menu? get contextMenu {