Fix Java::JavaLang::StringIndexOutOfBoundsException on ctx.cipher=[]

Author: MariuszCwikla

src/main/java/org/jruby/ext/openssl/CipherStrings.java

@@ -512,8 +512,10 @@ static Collection<Def> matchingCiphers(final String cipherString, final String[]
             }
 
             int index = 0;
-            switch ( part.charAt(0) ) {
-                case '!': case '+': case '-': index++; break;
+            if (part.length() > 0) {
+                switch ( part.charAt(0) ) {
+                    case '!': case '+': case '-': index++; break;
+                }
             }
 
             final Collection<Def> matching;

src/test/ruby/ssl/test_context.rb

@@ -178,4 +178,12 @@ def test_context_ciphers
     assert_equal [], diff
   end unless java7? # would need to filter out stuff such as ECDHE-RSA-AES128-GCM-SHA256
 
+  def test_set_ciphers_empty_array
+    context = OpenSSL::SSL::SSLContext.new
+    ex = assert_raise(OpenSSL::SSL::SSLError) do
+      context.ciphers = []
+    end
+    assert_equal "no cipher match", ex.message
+  end
+
 end