Add nil check in bind and a test

sqlite3.go

@@ -1511,11 +1511,15 @@ func (s *SQLiteStmt) bind(args []namedValue) error {
 		case float64:
 			rv = C.sqlite3_bind_double(s.s, n, C.double(v))
 		case []byte:
-			ln := len(v)
-			if ln == 0 {
-				v = placeHolder
+			if v == nil {
+				rv = C.sqlite3_bind_null(s.s, n)
+			} else {
+				ln := len(v)
+				if ln == 0 {
+					v = placeHolder
+				}
+				rv = C._sqlite3_bind_blob(s.s, n, unsafe.Pointer(&v[0]), C.int(ln))
 			}
-			rv = C._sqlite3_bind_blob(s.s, n, unsafe.Pointer(&v[0]), C.int(ln))
 		case time.Time:
 			b := []byte(v.Format(SQLiteTimestampFormats[0]))
 			rv = C._sqlite3_bind_text(s.s, n, (*C.char)(unsafe.Pointer(&b[0])), C.int(len(b)))