[SMTChecker] Fix compound assignment to push

test/libsolidity/smtCheckerTests/array_members/push_as_lhs_compound_assignment.sol

@@ -0,0 +1,15 @@
+pragma experimental SMTChecker;
+
+contract C {
+
+	int[] u;
+
+	function t() public {
+		require(u.length == 0);
+		u.push() -= 1;
+		assert(u[0] < 0); // should hold
+		assert(u[0] >= 0); // should fail
+	}
+}
+// ----
+// Warning 6328: (161-178): CHC: Assertion violation happens here.\nCounterexample:\nu = [(- 1)]\n\nTransaction trace:\nC.constructor()\nState: u = []\nC.t()