Guard NSString.UTF8String against nil in ExecuTorchModule.mm

Differential Revision: D105904682

Pull Request resolved: pytorch#19712

Author: metascroy

extension/apple/ExecuTorch/Exported/ExecuTorchModule.mm

@@ -319,7 +319,7 @@ - (BOOL)isLoaded {
 
 - (BOOL)loadMethod:(NSString *)methodName
              error:(NSError **)error {
-  const auto errorCode = _module->load_method(methodName.UTF8String);
+  const auto errorCode = _module->load_method(methodName.UTF8String ?: "");
   if (errorCode != Error::Ok) {
     if (error) {
       *error = ExecuTorchErrorWithCode((ExecuTorchErrorCode)errorCode);
@@ -363,7 +363,7 @@ - (BOOL)loadMethod:(NSString *)methodName
   // passed through to program_->load_method and is not cached on the C++
   // Module. ARC keeps `options` alive for the duration of this call via
   // the parameter, so no extra retention is needed here.
-  const auto errorCode = _module->load_method(methodName.UTF8String,
+  const auto errorCode = _module->load_method(methodName.UTF8String ?: "",
                                                /*planned_memory=*/nullptr,
                                                /*event_tracer=*/nullptr,
                                                [options cppMap]);
@@ -377,11 +377,11 @@ - (BOOL)loadMethod:(NSString *)methodName
 }
 
 - (BOOL)isMethodLoaded:(NSString *)methodName {
-  return _module->is_method_loaded(methodName.UTF8String);
+  return _module->is_method_loaded(methodName.UTF8String ?: "");
 }
 
 - (BOOL)unloadMethod:(NSString *)methodName {
-  const auto didUnload = _module->unload_method(methodName.UTF8String);
+  const auto didUnload = _module->unload_method(methodName.UTF8String ?: "");
   [_inputs removeObjectForKey:methodName];
   [_outputs removeObjectForKey:methodName];
   return didUnload;
@@ -404,7 +404,7 @@ - (BOOL)unloadMethod:(NSString *)methodName {
 
 - (nullable ExecuTorchMethodMetadata *)methodMetadata:(NSString *)methodName
                                                 error:(NSError **)error {
-  const auto result = _module->method_meta(methodName.UTF8String);
+  const auto result = _module->method_meta(methodName.UTF8String ?: "");
   if (!result.ok()) {
     if (error) {
       *error = ExecuTorchErrorWithCode((ExecuTorchErrorCode)result.error());
@@ -549,7 +549,7 @@ - (BOOL)setInput:(ExecuTorchValue *)value
        forMethod:(NSString *)methodName
          atIndex:(NSInteger)index
            error:(NSError **)error {
-  const auto errorCode = _module->set_input(methodName.UTF8String, toEValue(value), index);
+  const auto errorCode = _module->set_input(methodName.UTF8String ?: "", toEValue(value), index);
   if (errorCode != Error::Ok) {
     if (error) {
       *error = ExecuTorchErrorWithCode((ExecuTorchErrorCode)errorCode);
@@ -589,7 +589,7 @@ - (BOOL)setInputs:(NSArray<ExecuTorchValue *> *)values
   for (ExecuTorchValue *value in values) {
     inputs.push_back(toEValue(value));
   }
-  const auto errorCode = _module->set_inputs(methodName.UTF8String, inputs);
+  const auto errorCode = _module->set_inputs(methodName.UTF8String ?: "", inputs);
   if (errorCode != Error::Ok) {
     if (error) {
       *error = ExecuTorchErrorWithCode((ExecuTorchErrorCode)errorCode);
@@ -632,7 +632,7 @@ - (BOOL)setOutput:(ExecuTorchValue *)value
         forMethod:(NSString *)methodName
           atIndex:(NSInteger)index
             error:(NSError **)error {
-  const auto errorCode = _module->set_output(methodName.UTF8String, toEValue(value), index);
+  const auto errorCode = _module->set_output(methodName.UTF8String ?: "", toEValue(value), index);
   if (errorCode != Error::Ok) {
     if (error) {
       *error = ExecuTorchErrorWithCode((ExecuTorchErrorCode)errorCode);