UTFT 480x320 issue in compiling

I am facing errors in compiling Demo sketch from UTFT Lib:

-------- Please see below the errors faced ------
Warning: Board breadboard:avr:atmega328bb doesn't define a 'build.board' preference. Auto-set to: AVR_ATMEGA328BB
C:\Users\Nasa747W7\Documents\Arduino\libraries\UTFT-master\DefaultFonts.c:21:14: error: variable 'SmallFont' must be const in order to be put into read-only section by means of '__attribute__((progmem))'

fontdatatype SmallFont[1144] PROGMEM={

^

C:\Users\Nasa747W7\Documents\Arduino\libraries\UTFT-master\DefaultFonts.c:125:14: error: variable 'BigFont' must be const in order to be put into read-only section by means of '__attribute__((progmem))'

fontdatatype BigFont[3044] PROGMEM={

^

C:\Users\Nasa747W7\Documents\Arduino\libraries\UTFT-master\DefaultFonts.c:234:14: error: variable 'SevenSegNumFont' must be const in order to be put into read-only section by means of '__attribute__((progmem))'

fontdatatype SevenSegNumFont[2004] PROGMEM={

^

exit status 1
Error compiling for board Arduino/Genuino Mega or Mega 2560.

Start by compiling the UTFT Demo sketch for the Arduino/Genuino Mega or Mega 2560 and inspect DefaultFonts.c at the SmallFont, BigFont, and SevenSegNumFont declarations. Done means the Demo sketch compiles without the reported PROGMEM errors.

Written by the indexing model from the issue text.