Account for possibly empty license_template_path

Don't attempt to load license_template if the path wasn't specified.

src/config/config_type.rs

@@ -392,6 +392,7 @@ macro_rules! create_config {
             }
 
             fn set_license_template(&mut self) {
+                if self.was_set().license_template_path() {
                     let license_template_path = self.license_template_path();
                     let mut license_template_file = match File::open(&license_template_path) {
                         Ok(file) => file,
@@ -425,6 +426,7 @@ macro_rules! create_config {
                     }
                 }
             }
+        }
 
         // Template for the default configuration
         impl Default for Config {