QL: Add query that finds 'if p() then q() else none()'.

ql/src/queries/style/IfWithElseNone.ql

@@ -0,0 +1,15 @@
+/**
+ * @name Use of 'if' with a 'none()' branch.
+ * @description Using 'if p() then q() else none()' is bad style. It should be rewritten as 'p() and q()'.
+ * @kind problem
+ * @problem.severity warning
+ * @id ql/if-with-none
+ * @precision very-high
+ * @tags maintainability
+ */
+
+import ql
+
+from IfFormula ifFormula
+where ifFormula.getElsePart() instanceof NoneCall or ifFormula.getThenPart() instanceof NoneCall
+select ifFormula, "Use a conjunction instead."