Fix wrong exception when running SQL while in #copy_data for output.

It raised "undefined method `result_status' for nil:NilClass" previously
and raises "no COPY in progress" now.

This also fixes the failing test of the previous commit.

History.rdoc

@@ -19,6 +19,8 @@ Enhancements:
 Bugfixes:
 - Release GVL while calling PQsetClientEncoding(). #245
 - Add __EXTENSIONS__ to Solaris/SmartOS for Ruby >= 2.3.x. #236
+- Fix wrong exception when running SQL while in Connection#copy_data
+  block for output
 
 
 == v0.18.4 [2015-11-13] Michael Granger <ged@FaerieMUD.org>

lib/pg/connection.rb

@@ -186,7 +186,7 @@ def copy_data( sql, coder=nil )
 				raise
 			else
 				res = get_last_result
-				if res.result_status != PGRES_COMMAND_OK
+				if !res || res.result_status != PGRES_COMMAND_OK
 					while get_copy_data
 					end
 					while get_result