v3.1.0: added a new type of standard room to replace empty ones

SPD-classes/src/main/java/com/watabou/utils/Random.java

@@ -171,19 +171,24 @@ public class Random {
 	}
 
 	//returns an index from chances, the probability of each index is the weight values in changes
+	//negative values are treated as 0
 	public static int chances( float[] chances ) {
 		
 		int length = chances.length;
 		
 		float sum = 0;
 		for (int i=0; i < length; i++) {
-			sum += chances[i];
+			sum += Math.max(0, chances[i]);
+		}
+
+		if (sum <= 0){
+			return -1;
 		}
 		
 		float value = Float( sum );
 		sum = 0;
 		for (int i=0; i < length; i++) {
-			sum += chances[i];
+			sum += Math.max(0, chances[i]);
 			if (value < sum) {
 				return i;
 			}