fonts: Dont memcpy with nullptr in SkRemoteGlyphCache
fonts: Dont memcpy with nullptr in SkRemoteGlyphCache

The behaviour is undefined and causes ASAN bots to complain.

Bug: skia:7515
Change-Id: I454714ab9047a6fced5ab7bfdbc12214d728eadf
Reviewed-on: https://skia-review.googlesource.com/125029
Reviewed-by: Brian Osman <794c0b5534edf5601d88e1d41975d0262da12894@google.com>
Commit-Queue: Khusal Sagar <7c3e7b6b198ace4145f09ef7c4cf18c84ce8661e@chromium.org>

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