Fix clang compilation error introduced in r1380.

Fixes:
  .../linux_dumper.cc:308:25: error: address of array 'module->name' will always evaluate to 'true' [-Werror,-Wpointer-bool-conversion]
                module->name && module->name[0] == '/' &&
                ~~~~~~~~^~~~

BUG=chromium:394703
R=rmcilroy@chromium.org

Review URL: https://breakpad.appspot.com/5724002

Patch from Simon Baldwin <simonb@chromium.org>.

git-svn-id: http://google-breakpad.googlecode.com/svn/trunk@1384 4c0a9323-5329-0410-9bdc-e9ce6186880e