Add parameter type check when initializing Mysql2::Client (brianmario#792)

Fix for segfault when initializing a Mysql2::Client reported in issue brianmario#782

Author: braxtone

.rubocop.yml

@@ -22,6 +22,15 @@ Style/TrailingComma:
 Style/TrivialAccessors:
   AllowPredicates: true
 
+Metrics/AbcSize:
+  Max: 82
+
+Metrics/CyclomaticComplexity:
+  Max: 28
+
+Metrics/MethodLength:
+  Max: 55
+
 # TODO: remove when we end support for < 1.9.3
 
 Style/HashSyntax:

lib/mysql2/client.rb

@@ -19,6 +19,7 @@ def self.default_query_options
     end
 
     def initialize(opts = {})
+      fail Mysql2::Error, "Options parameter must be a Hash" unless opts.is_a? Hash
       opts = Mysql2::Util.key_hash_as_symbols(opts)
       @read_timeout = nil
       @query_options = self.class.default_query_options.dup