Fix Directory.dir_exist/get_current_dir for 'res://' on Android

Fix #7014

(cherry picked from commit 8d454ed9a7)

platform/android/java/src/org/godotengine/godot/GodotIO.java

@@ -288,6 +288,11 @@ public class GodotIO {
 
 		try {
 			ad.files = am.list(path);
+			// no way to find path is directory or file exactly.
+			// but if ad.files.length==0, then it's an empty directory or file.
+			if (ad.files.length==0) {
+				return -1;
+			}
 		} catch (IOException e) {
 
 			System.out.printf("Exception on dir_open: %s\n",e);