Type Checker: Fix internal error when applying unary operators to tuples with empty components

test/libsolidity/syntaxTests/iceRegressionTests/declarationUnaryTuple/declaration_delete_tuple.sol

@@ -0,0 +1,10 @@
+contract C
+{
+    function f() public
+    {
+        int x = delete (,0);
+    }
+}
+// ----
+// TypeError: (68-69): Expression has to be an lvalue.
+// TypeError: (59-70): Unary operator delete cannot be applied to type tuple(,int_const 0)