[rubygems/rubygems] Fix `bundle platform` crash when there's a lockfile with no Ruby locked

https://github.com/rubygems/rubygems/commit/49fc54e87d

lib/bundler/cli/platform.rb

@@ -9,7 +9,7 @@ module Bundler
 
     def run
       platforms, ruby_version = Bundler.ui.silence do
-        locked_ruby_version = Bundler.locked_gems && Bundler.locked_gems.ruby_version.gsub(/p\d+\Z/, "")
+        locked_ruby_version = Bundler.locked_gems && Bundler.locked_gems.ruby_version&.gsub(/p\d+\Z/, "")
         gemfile_ruby_version = Bundler.definition.ruby_version && Bundler.definition.ruby_version.single_version_string
         [Bundler.definition.platforms.map {|p| "* #{p}" },
          locked_ruby_version || gemfile_ruby_version]

spec/bundler/commands/platform_spec.rb

@@ -234,6 +234,29 @@ G
       expect(out).to eq("ruby 1.0.0")
     end
 
+    it "handles when there is a lockfile with no requirement" do
+      gemfile <<-G
+        source "#{file_uri_for(gem_repo1)}"
+      G
+
+      lockfile <<-L
+        GEM
+          remote: #{file_uri_for(gem_repo1)}/
+          specs:
+
+        PLATFORMS
+          ruby
+
+        DEPENDENCIES
+
+        BUNDLED WITH
+           #{Bundler::VERSION}
+      L
+
+      bundle "platform --ruby"
+      expect(out).to eq("No ruby version specified")
+    end
+
     it "handles when there is a requirement in the gemfile" do
       gemfile <<-G
         source "#{file_uri_for(gem_repo1)}"