engine: fix NULL ptr dereference when log file cannot be opened

engine/common/sys_con.c

@@ -113,11 +113,16 @@ void Sys_InitLog( void )
 	if( s_ld.log_active )
 	{
 		s_ld.logfile = fopen( s_ld.log_path, mode );
-		if( !s_ld.logfile ) Con_Reportf( S_ERROR  "Sys_InitLog: can't create log file %s\n", s_ld.log_path );
-
-		fprintf( s_ld.logfile, "=================================================================================\n" );
-		fprintf( s_ld.logfile, "\t%s (build %i) started at %s\n", s_ld.title, Q_buildnum(), Q_timestamp( TIME_FULL ));
-		fprintf( s_ld.logfile, "=================================================================================\n" );
+		if( !s_ld.logfile )
+		{
+			Con_Reportf( S_ERROR  "Sys_InitLog: can't create log file %s\n", s_ld.log_path );
+		}
+		else
+		{
+			fprintf( s_ld.logfile, "=================================================================================\n" );
+			fprintf( s_ld.logfile, "\t%s (build %i) started at %s\n", s_ld.title, Q_buildnum(), Q_timestamp( TIME_FULL ));
+			fprintf( s_ld.logfile, "=================================================================================\n" );
+		}
 	}
 }