macOS: fix a crash when dragging non-file content onto window

Winit only supports text, thus we should ignore the rest
instead of crashing.

winit-appkit/src/window_delegate.rs

@@ -353,13 +353,16 @@ define_class!(
             use std::path::PathBuf;
 
             let pb = sender.draggingPasteboard();
+
             #[allow(deprecated)]
-            let filenames = pb
-                .propertyListForType(unsafe { NSFilenamesPboardType })
-                .unwrap()
+            let property_list = match pb.propertyListForType(unsafe { NSFilenamesPboardType }) {
+                Some(property_list) => property_list,
+                None => return false.into(),
+            };
+
+            let paths = property_list
                 .downcast::<NSArray>()
-                .unwrap();
-            let paths = filenames
+                .unwrap()
                 .into_iter()
                 .map(|file| PathBuf::from(file.downcast::<NSString>().unwrap().to_string()))
                 .collect();
@@ -411,13 +414,16 @@ define_class!(
             use std::path::PathBuf;
 
             let pb = sender.draggingPasteboard();
+
             #[allow(deprecated)]
-            let filenames = pb
-                .propertyListForType(unsafe { NSFilenamesPboardType })
-                .unwrap()
+            let property_list = match pb.propertyListForType(unsafe { NSFilenamesPboardType }) {
+                Some(property_list) => property_list,
+                None => return false.into(),
+            };
+
+            let paths = property_list
                 .downcast::<NSArray>()
-                .unwrap();
-            let paths = filenames
+                .unwrap()
                 .into_iter()
                 .map(|file| PathBuf::from(file.downcast::<NSString>().unwrap().to_string()))
                 .collect();

winit/src/changelog/unreleased.md

@@ -272,3 +272,4 @@ changelog entry.
 - On Web, device events are emitted regardless of cursor type.
 - On Wayland, `axis_value120` scroll events now generate `MouseScrollDelta::LineDelta`
 - On X11, mouse scroll button events no longer cause duplicated `WindowEvent::MouseWheel` events.
+- On macOS, fixed crash when dragging non-file content onto window.