NestedIfJoinLinesHandler: fix polyadic case.

Fixes IDEA-190660 ClassCastException after code reformatting using 'Join Lines'
Fixes EA-119515 - CCE: NestedIfJoinLinesHandler.tryJoinLines

java/java-tests/testData/codeInsight/joinLines/IfChainPolyadic_after.java

@@ -0,0 +1,5 @@
+class Foo {
+    void test(int a, int b) {
+        if(a > 0 && a < 10 <caret>&& b > 0 && b < 10) System.out.println(a + b);
+    }
+}