Panic challenge accepted ;)

```sh
$ mysql -e "SELECT '' '' ''"
+--+
|  |
+--+
|  |
+--+
```
```sh
$ mysql -e "SELECT 'a' 'b' 'c' 'd'"
+------+
| a    |
+------+
| abcd |
+------+
```

```sh
$ go test
----------------------------------------------------------------------
PANIC: query_test.go:434: TestSuite.TestFingerprintPanicChallenge1

... Panic: runtime error: index out of range (PC=0x40EADD)

/usr/local/go/src/pkg/runtime/panic.c:248
  in panic
/usr/local/go/src/pkg/runtime/panic.c:552
  in panicstring
/usr/local/go/src/pkg/runtime/panic.c:466
  in panicindex
query.go:366
  in Fingerprint
query_test.go:439
  in TestSuite.TestFingerprintPanicChallenge1

----------------------------------------------------------------------
PANIC: query_test.go:445: TestSuite.TestFingerprintPanicChallenge2

... Panic: runtime error: index out of range (PC=0x40EADD)

/usr/local/go/src/pkg/runtime/panic.c:248
  in panic
/usr/local/go/src/pkg/runtime/panic.c:552
  in panicstring
/usr/local/go/src/pkg/runtime/panic.c:466
  in panicindex
query.go:174
  in Fingerprint
query_test.go:450
  in TestSuite.TestFingerprintPanicChallenge2
OOPS: 7 passed, 2 PANICKED
--- FAIL: Test (0.00 seconds)
FAIL
exit status 1
FAIL	github.com/percona/go-mysql/query	0.002s
```