example/dodge_the_creeps: Replace unsafe code

This merge request replaces the currently used `unsafe` code with safe
implementation using `get_viewport_rect`

Discovered during quality assurance for RXT0147/unnamedGame#1

Signed-off-by: Jacob Hrbek <[email protected]>

Author: Kreyren

examples/dodge_the_creeps/src/player.rs

@@ -32,8 +32,8 @@ impl Player {
 
     #[export]
     fn _ready(&mut self, owner: &Area2D) {
-        let viewport = unsafe { owner.get_viewport().unwrap().assume_safe() };
-        self.screen_size = viewport.size();
+        let viewport = owner.get_viewport_rect();
+        self.screen_size = viewport.size.to_vector();
         owner.hide();
     }