HWC2: Don't set null handle for client layers

Removes the code that explicitly set a null buffer handle for client
layers.

Bug: 29463310
Change-Id: I570e6041ba72d64971bb6c364e8e7b6f84eeff08
diff --git a/services/surfaceflinger/Layer.cpp b/services/surfaceflinger/Layer.cpp
index d732c07..6c78000 100644
--- a/services/surfaceflinger/Layer.cpp
+++ b/services/surfaceflinger/Layer.cpp
@@ -726,11 +726,6 @@
         // setup a solid color layer yet
         ALOGV("[%s] Requesting Client composition", mName.string());
         setCompositionType(hwcId, HWC2::Composition::Client);
-        error = hwcLayer->setBuffer(nullptr, Fence::NO_FENCE);
-        if (error != HWC2::Error::None) {
-            ALOGE("[%s] Failed to set null buffer: %s (%d)", mName.string(),
-                    to_string(error).c_str(), static_cast<int32_t>(error));
-        }
         return;
     }