Do not create empty color table if it does not exist

src/codec/SkCodec_libbmp.cpp

Index: src/codec/SkCodec_libbmp.cpp
diff --git a/src/codec/SkCodec_libbmp.cpp b/src/codec/SkCodec_libbmp.cpp
index 62cda95733c97bc2c90bbe71e538800257b61d77..e9551cbb6ff098338da2ec16383488b6332702a3 100644
--- a/src/codec/SkCodec_libbmp.cpp
+++ b/src/codec/SkCodec_libbmp.cpp
@@ -570,7 +570,9 @@ SkCodec::Result SkBmpCodec::onGetPixels(const SkImageInfo& dstInfo,
     }
 
     // Set the color table and return true on success
-    fColorTable.reset(SkNEW_ARGS(SkColorTable, (colorTable, maxColors)));
+    if (maxColors > 0) {
+        fColorTable.reset(SkNEW_ARGS(SkColorTable, (colorTable, maxColors)));
+    }
     return true;
 }