better fix...

lib/pry/default_commands/gems.rb

@@ -59,7 +59,7 @@ class Pry
         BANNER
 
         def process(pattern=nil)
-          pattern = Regexp.compile(pattern)
+          pattern = Regexp.compile(pattern || '')
           gems    = if Gem::Specification.respond_to?(:each)
                       Gem::Specification.select{|spec| spec.name =~ pattern }.group_by(&:name)
                     else

test/test_default_commands/test_gems.rb

@@ -7,7 +7,7 @@ describe "Pry::DefaultCommands::Gems" do
     it 'should not raise when invoked' do
       str_output = StringIO.new
       Pry.start self, :input => InputTester.new("gem-list", "exit-all"), :output => str_output
-      str_output.string.should.not =~ /NoMethodError/
+      str_output.string.should.not =~ /Error/
     end
 
     it 'should not raise when invoked with an argument' do