protect against fuzzer
protect against fuzzer

Fuzzer data may generate path without a computable
length.

R=f5cabf8735907151a446812c9875d6c0c712d847@google.com
Bug: 739190
Change-Id: I052540932937f24951ce66699080b8b959fb1a46
Reviewed-on: https://skia-review.googlesource.com/21500
Reviewed-by: Mike Reed <f5cabf8735907151a446812c9875d6c0c712d847@google.com>
Commit-Queue: Cary Clark <52792aa984ff6c4e9c802c7fa3093ed6a52a791f@google.com>

rubenvb/skia,aosp-mirror/platform_external_skia,rubenvb/skia,Hikari-no-Tenshi/android_external_skia,google/skia,HalCanary/skia-hc,Hikari-no-Tenshi/android_external_skia,HalCanary/skia-hc,Hikari-no-Tenshi/android_external_skia,HalCanary/skia-hc,rubenvb/skia,rubenvb/skia,HalCanary/skia-hc,HalCanary/skia-hc,google/skia,HalCanary/skia-hc,aosp-mirror/platform_external_skia,google/skia,aosp-mirror/platform_external_skia,rubenvb/skia,aosp-mirror/platform_external_skia,rubenvb/skia,rubenvb/skia,aosp-mirror/platform_external_skia,google/skia,aosp-mirror/platform_external_skia,Hikari-no-Tenshi/android_external_skia,Hikari-no-Tenshi/android_external_skia,google/skia,google/skia,Hikari-no-Tenshi/android_external_skia,google/skia,aosp-mirror/platform_external_skia,HalCanary/skia-hc,rubenvb/skia,rubenvb/skia,HalCanary/skia-hc,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,HalCanary/skia-hc,rubenvb/skia,google/skia,Hikari-no-Tenshi/android_external_skia,HalCanary/skia-hc,google/skia,google/skia,Hikari-no-Tenshi/android_external_skia