Make sure running bin/spring does not add an empty string to Gem.path.

An empty string in `Gem.path` causes issues in third party gems like rvm or better_errors. See #297 and #310.

This happens because `Gem.paths=` picks up `$GEM_HOME` even if it’s set to an empty string. Fixed by unsetting `$GEM_HOME`.

Author: noniq

CHANGELOG.md

@@ -1,5 +1,7 @@
 ## Next version
 
+* Make sure running `bin/spring` does not add an empty string to `Gem.path`.
+  Issues #297, #310.
 * Fixed problem with `$0` including the command line args, which could
   confuse commands which try to parse `$0`. This caused the
   spring-commands-rspec to not work properly in some cases. Issue #369.

lib/spring/client/binstub.rb

@@ -38,7 +38,7 @@ class Binstub < Command
 
   if match = Bundler.default_lockfile.read.match(/^GEM$.*?^    (?:  )*spring \((.*?)\)$.*?^$/m)
     ENV["GEM_PATH"] = ([Bundler.bundle_path.to_s] + Gem.path).join(File::PATH_SEPARATOR)
-    ENV["GEM_HOME"] = ""
+    ENV["GEM_HOME"] = nil
     Gem.paths = ENV
 
     gem "spring", match[1]