Implement 'apply' for Option<EnvFile>

src/env_file.rs

@@ -149,6 +149,14 @@ impl <E> ApplyEnvironmentFile for Result<EnvironmentFile, E> {
     }
 }
 
+impl ApplyEnvironmentFile for Option<EnvironmentFile> {
+	fn apply(&self, options: ApplyOptions) {
+        if let Some(file) = self {
+            file.apply(options);
+        }
+    }
+}
+
 pub struct EnvFileIterator<'a> {
 	lines: &'a [FileLine],
 	current: usize,