param.BigRational: fix isInteger()

We have to compare the denominator to BigInteger.ONE instead of
BigRational.ONE...

Introduced in SVN 11554.


git-svn-id: https://www.prismmodelchecker.org/svn/prism/prism/trunk@11596 bbc10eb1-c90d-0410-af57-cb519fbb1720

prism/src/param/BigRational.java

@@ -783,7 +783,7 @@ public final class BigRational implements Comparable<BigRational>
 	 */
 	public boolean isInteger()
 	{
-		return isRational() && getDen().equals(ONE);
+		return isRational() && getDen().equals(BigInteger.ONE);
 	}
 
 	/**