Warn about missing MySQL encoding mappings

and fix a bug mapping them to "" instead of NULL.

Author: felixbuenemann

support/mysql_enc_to_ruby.rb

@@ -52,7 +52,10 @@
 
 collations.each do |collation|
   mysql_col_idx = collation[2].to_i
-  rb_enc = mysql_to_rb[collation[1]]
+  rb_enc = mysql_to_rb.fetch(collation[1]) do |mysql_enc|
+    $stderr.puts "WARNING: Missing mapping for collation \"#{collation[0]}\" with encoding \"#{mysql_enc}\" and id #{mysql_col_idx}, assuming NULL"
+    "NULL"
+  end
   encodings[mysql_col_idx - 1] = [mysql_col_idx, rb_enc]
 end