Fix ICU support data loading

This fixes an error in loading the ICU support data on platforms that
don't use either the builtin icu4c or the static ICU support data.

modules/text_server_adv/text_server_adv.cpp

@@ -442,6 +442,8 @@ bool TextServerAdvanced::_load_support_data(const String &p_filename) {
 	}
 #else
 	if (!icu_data_loaded) {
+		UErrorCode err = U_ZERO_ERROR;
+#ifdef ICU_DATA_NAME
 		String filename = (p_filename.is_empty()) ? String("res://") + _MKSTR(ICU_DATA_NAME) : p_filename;
 
 		Ref<FileAccess> f = FileAccess::open(filename, FileAccess::READ);
@@ -451,13 +453,13 @@ bool TextServerAdvanced::_load_support_data(const String &p_filename) {
 		uint64_t len = f->get_length();
 		icu_data = f->get_buffer(len);
 
-		UErrorCode err = U_ZERO_ERROR;
 		udata_setCommonData(icu_data.ptr(), &err);
 		if (U_FAILURE(err)) {
 			ERR_FAIL_V_MSG(false, u_errorName(err));
 		}
 
 		err = U_ZERO_ERROR;
+#endif
 		u_init(&err);
 		if (U_FAILURE(err)) {
 			ERR_FAIL_V_MSG(false, u_errorName(err));