Fix ICE when bitwise operator on fixed bytes

test/libsolidity/smtCheckerTests/operators/bitwise_and_fixed_bytes.sol

@@ -0,0 +1,8 @@
+pragma experimental SMTChecker;
+contract C {
+  function f() public pure returns (byte) {
+    return (byte("") & (""));
+  }
+}
+// ----
+// Warning 5084: (101-109): Type conversion is not yet fully supported and might yield false positives.

test/libsolidity/smtCheckerTests/operators/bitwise_xor_fixed_bytes.sol

@@ -0,0 +1,9 @@
+pragma experimental SMTChecker;
+contract Simp {
+    function f3() public pure returns (byte) {
+        bytes memory y = "def";
+        return y[0] ^ "e";
+    }
+}
+// ----
+// Warning 1093: (142-152): Assertion checker does not yet implement this bitwise operator.