Check upload name to make sure its an image or video

The upload code should be additionally refactored to probably do a more
comprehensive check of if the file is an image or video.

src/files.rs

@@ -1,4 +1,3 @@
-use std::ffi::OsStr;
 use std::fs::read_dir;
 use std::io;
 use std::io::Error;
@@ -22,13 +21,11 @@ pub fn list_files(dir: PathBuf) -> io::Result<Vec<PathBuf>> {
     Ok(files)
 }
 
-fn is_image_or_video(path: &Path) -> bool {
-    let extension = &path
+pub fn is_image_or_video(path: &Path) -> bool {
+    let extension = path
         .extension()
-        .unwrap_or_else(|| OsStr::new(""))
-        .to_str()
-        .unwrap_or("")
-        .to_lowercase();
+        .and_then(|p| p.to_str())
+        .map_or(String::from(""), |p| p.to_lowercase());
 
     extension == "png"
         || extension == "jpg"