Cannot convert ‘bool’ to ‘NEDElement*’

During installation of Omnetpp ,in final step "make" ,I encountered an error which says

**`cannot convert ‘bool’ to ‘NEDElement`**   in return  np->getErrors()->addError("", "unable to allocate work memory"); return false;}Makefile:51: recipe for target '/home/shivanshu/Desktop/FinalProject/omnetpp-4.2.2/out/gcc-release/src/nedxml/ned2.tab.o' failedmake[2]: *** [/home/shivanshu/Desktop/FinalProject/omnetpp-4.2.2/out/gcc-release/src/nedxml/ned2.tab.o] Error 1make[2]: Leaving directory '/home/shivanshu/Desktop/FinalProject/omnetpp-4.2.2/src/nedxml'Makefile:96: recipe for target 'nedxml' failedmake[1]: *** [nedxml] Error 2make[1]: Leaving directory '/home/shivanshu/Desktop/FinalProject/omnetpp-4.2.2'Makefile:19: recipe for target 'allmodes' failedmake: *** [allmodes] Error 2

The corresponding function is as below in which sometimes it is returning the type NEDElement * type and sometimes it's returning bool.

NEDElement *doParseNED2(NEDParser *p, const char *nedtext){#if YYDEBUG != 0      /* #if added --VA */    yydebug = YYDEBUGGING_ON;#endif    NONREENTRANT_NED_PARSER(p);    // reset the lexer    pos.co = 0;    pos.li = 1;    prevpos = pos;    yyin = NULL;    yyout = stderr; // not used anyway    // alloc buffer    struct yy_buffer_state *handle = yy_scan_string(nedtext);    if (!handle)        {np->getErrors()->addError("", "unable to allocate work memory"); return false;}    // create parser state and NEDFileElement    resetParserState();    ps.nedfile = new NedFileElement();    // store file name with slashes always, even on Windows -- neddoc relies on that    ps.nedfile->setFilename(slashifyFilename(np->getFileName()).c_str());    ps.nedfile->setVersion("2");    // storing the start and end position of the whole file for the NedFileElement    // NOTE: we cannot use storePos() because it strips off the leading spaces    // and comments from the element.    YYLTYPE pos = np->getSource()->getFullTextPos();    NEDSourceRegion region;    region.startLine = pos.first_line;    region.startColumn = pos.first_column;    region.endLine = pos.last_line;    region.endColumn = pos.last_column;    ps.nedfile->setSourceRegion(region);    // store file comment    storeFileComment(ps.nedfile);    ps.propertyscope.push(ps.nedfile);    globalps = ps; // remember this for error recovery    if (np->getStoreSourceFlag())        storeSourceCode(ps.nedfile, np->getSource()->getFullTextPos());    // parse    try    {        yyparse();    }    catch (NEDException& e)    {        yyerror((std::string("error during parsing: ")+e.what()).c_str());        yy_delete_buffer(handle);        return 0;    }    if (np->getErrors()->empty())    {        // more sanity checks        if (ps.propertyscope.size()!=1 || ps.propertyscope.top()!=ps.nedfile)            INTERNAL_ERROR0(NULL, "error during parsing: imbalanced propertyscope");        if (!ps.blockscope.empty() || !ps.typescope.empty())            INTERNAL_ERROR0(NULL, "error during parsing: imbalanced blockscope or typescope");    }    yy_delete_buffer(handle);    return ps.nedfile;}

I searched it on internet but i found ,you should have a latest gcc version ,but already i have gcc version 7.5.

Please help.