fix floating panels and iOS export picking

src/util.cpp

@@ -577,6 +577,8 @@ std::wstring str2wstr(const std::string& str)
     //const char* ptr = str.c_str();
     //std::mbsrtowcs((wchar_t*)converted.data(), &ptr, converted.capacity(), &st);
     //return converted;
+    if (str.empty())
+        return {};
     using convert_typeX = std::codecvt_utf8<wchar_t>;
     std::wstring_convert<convert_typeX, wchar_t> converterX;
     return converterX.from_bytes(str);
@@ -590,6 +592,8 @@ std::string wstr2str(const std::wstring & wstr)
     //const wchar_t * wptr = wstr.c_str();
     //std::wcsrtombs((char*)converted.data(), &wptr, converted.capacity(), &st);
     //return converted;
+    if (wstr.empty())
+        return {};
     using convert_typeX = std::codecvt_utf8<wchar_t>;
     std::wstring_convert<convert_typeX, wchar_t> converterX;
     return converterX.to_bytes(wstr);