Update Thread#thread_variable_get to match Ruby 3.4 behaviour

spec/core/thread/thread_variable_get_spec.rb

@@ -48,17 +48,13 @@
 
   ruby_version_is '3.4' do
     it "raises a TypeError if the key is neither Symbol nor String when no thread variables are set" do
-      NATFIXME 'it raises a TypeError if the key is neither Symbol nor String when no thread variables are set', exception: SpecFailedException do
-        -> { @t.thread_variable_get(123) }.should raise_error(TypeError, /123 is not a symbol/)
-      end
+      -> { @t.thread_variable_get(123) }.should raise_error(TypeError, /123 is not a symbol/)
     end
 
     it "raises a TypeError if the key is neither Symbol nor String without calling #to_sym" do
       key = mock('key')
-      NATFIXME 'it raises a TypeError if the key is neither Symbol nor String without calling #to_sym', exception: SpecFailedException do
-        key.should_not_receive(:to_sym)
-        -> { @t.thread_variable_get(key) }.should raise_error(TypeError, /#{Regexp.escape(key.inspect)} is not a symbol/)
-      end
+      key.should_not_receive(:to_sym)
+      -> { @t.thread_variable_get(key) }.should raise_error(TypeError, /#{Regexp.escape(key.inspect)} is not a symbol/)
     end
   end
 end

src/thread_object.cpp

@@ -570,9 +570,9 @@ bool ThreadObject::has_thread_variable(Env *env, Value key) const {
 }
 
 Value ThreadObject::thread_variable_get(Env *env, Value key) {
+    key = validate_key(env, key);
     if (!m_thread_variables)
         return NilObject::the();
-    key = validate_key(env, key);
     return m_thread_variables->ref(env, key);
 }