'ArrayIndexOutOfBoundsException: Coordinate out of bounds!' when resizing sketch and saving frame

*Created by: clankill3r*

When resizing the sketch really small and saving frames an ArrayIndexOutOfBoundsException is triggered.

```java
void setup() {
  surface.setResizable(true); 
}

void draw() {
  saveFrame();  
}
```

alpha 3
OSX 10.15.7