Do not return null paint if shaderFP is null
Do not return null paint if shaderFP is null

This fixes the ripple bug reported by LG:
https://b.corp.google.com/issues/68964656

In that bug, the button is so tall that our image shader returns
a null fragment processor because the height exceeds GL_MAX_TEXTURE_SIZE.
If we return null paint, the ripple is completely gone. This CL returns
a default paint so we can still see the ripple, and that matches HWUI's
behaviour.

A GM will be added later after some other urgent Android ripple bug fixes.

Bug: skia:
Change-Id: I9bcafc078916a6a15fbd84d2019f39ac88d2b2f8
Reviewed-on: https://skia-review.googlesource.com/73200
Commit-Queue: Yuqian Li <5537666080209cb36918c342659e07eb122af24c@google.com>
Reviewed-by: Brian Salomon <61fabaaf0876044aeedfd8e351e485c028d69e7b@google.com>

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