Handle unbalanced quotes in environment field

Shellwords.split raises ArgumentError on malformed input (e.g. an
unbalanced quote like FOO="bar). Since build_rake_command runs in the
request thread before the fork, an unhandled raise surfaced as a 500.
Rescue the ArgumentError and treat malformed input as no usable env
tokens, then add a test covering the case.

Author: michelaquino

app/models/rake_ui/rake_task.rb

@@ -115,7 +115,17 @@ def build_rake_command(args: nil, environment: nil)
       if environment
         # Safely escape environment variables to prevent shell injection
         # Only accept KEY=VALUE pairs; reject malicious tokens
-        escaped_env = Shellwords.split(environment).map do |token|
+        #
+        # Shellwords.split raises ArgumentError on malformed input (e.g. an
+        # unbalanced quote like FOO="bar). Treat that as no usable env tokens
+        # rather than letting the exception bubble up as a 500.
+        tokens = begin
+          Shellwords.split(environment)
+        rescue ArgumentError
+          []
+        end
+
+        escaped_env = tokens.map do |token|
           next unless token.match?(/\A[A-Z_][A-Z0-9_]*=.+\z/i)
 
           # Valid KEY=VALUE pattern - escape only the value

test/rake_ui/rake_task_test.rb

@@ -49,6 +49,21 @@ class RakeTaskTest < ActiveSupport::TestCase
     assert_includes command, "rake", "Should include rake command"
   end
 
+  test "does not raise when environment contains an unbalanced quote" do
+    task = get_double_nested_task
+
+    # Shellwords.split raises ArgumentError on unbalanced quotes; this is called
+    # in the request thread before the fork, so an unhandled raise would 500.
+    unbalanced = 'FOO="bar'
+    command = nil
+    assert_nothing_raised do
+      command = task.build_rake_command(environment: unbalanced)
+    end
+
+    # Malformed env is dropped; the rake command is still produced.
+    assert_equal "rake #{task.name}", command
+  end
+
   test "escapes special shell characters in args" do
     task = get_double_nested_task