Fix Marshal.load with empty string argument

spec/ruby/core/marshal/shared/load.rb

@@ -8,7 +8,11 @@
 
   it "raises an ArgumentError when the dumped data is truncated" do
     obj = {first: 1, second: 2, third: 3}
-    -> { Marshal.send(@method, Marshal.dump(obj)[0, 5]) }.should raise_error(ArgumentError)
+    -> { Marshal.send(@method, Marshal.dump(obj)[0, 5]) }.should raise_error(ArgumentError, "marshal data too short")
+  end
+
+  it "raises an ArgumentError when the argument is empty String" do
+    -> { Marshal.send(@method, "") }.should raise_error(ArgumentError, "marshal data too short")
   end
 
   it "raises an ArgumentError when the dumped class is missing" do

src/main/ruby/truffleruby/core/marshal.rb

@@ -505,12 +505,7 @@ def initialize(stream, depth, proc)
         @stream = nil
       end
 
-      if stream
-        @consumed = 2
-      else
-        @consumed = 0
-      end
-
+      @consumed = 0
       @modules = nil
       @has_ivar = []
       @proc = proc
@@ -1327,12 +1322,10 @@ def self.dump(obj, an_io=nil, limit=nil)
   def self.load(obj, prc = nil)
     if Primitive.object_respond_to? obj, :to_str, false
       data = obj.to_s
-
-      major = data.getbyte 0
-      minor = data.getbyte 1
-
       ms = StringState.new data, nil, prc
 
+      major = ms.consume_byte
+      minor = ms.consume_byte
     elsif Primitive.object_respond_to? obj, :read, false and
           Primitive.object_respond_to? obj, :getc, false
       ms = IOState.new obj, nil, prc