Handle case where newline chars don't transcode to detected encoding

We've seen cases where binary files are detected as encodings such as
ISO-8859-8-I. This usually happens when the binary files are short, so
while the detector is mistaken, there is also not very much data for use
in the detection algorithm in the first place so it's understandable
that the detector was wrong.

In these cases, the code to convert ASCII newline characters to
encodings such as ISO-8859-8-I fails because there is no conversion
between them.

We now simply assume that the data is all one line in those cases. In
reality the data is binary, but this obviously difficult to detect
reliably.

lib/linguist/blob_helper.rb

@@ -256,10 +256,16 @@ module Linguist
           # without changing the encoding of `data`, and
           # also--importantly--without having to duplicate many (potentially
           # large) strings.
-          encoded_newlines = ["\r\n", "\r", "\n"].
-            map { |nl| nl.encode(encoding).force_encoding(data.encoding) }
+          begin
+            encoded_newlines = ["\r\n", "\r", "\n"].
+              map { |nl| nl.encode(encoding, "ASCII-8BIT").force_encoding(data.encoding) }
 
-          data.split(Regexp.union(encoded_newlines), -1)
+            data.split(Regexp.union(encoded_newlines), -1)
+          rescue Encoding::ConverterNotFoundError
+            # The data is not splittable in the detected encoding.  Assume it's
+            # one big line.
+            [data]
+          end
         else
           []
         end

samples/Text/iso8859-8-i.txt

@@ -0,0 +1 @@
+%<25><><EFBFBD>

test/test_blob.rb

@@ -97,6 +97,7 @@ class TestBlob < Test::Unit::TestCase
   def test_sloc
     assert_equal 2, blob("Ruby/foo.rb").sloc
     assert_equal 3, blob("Text/utf16le-windows.txt").sloc
+    assert_equal 1, blob("Text/iso8859-8-i.txt").sloc
   end
 
   def test_encoding