swfc mem_put_() crash

[lcatro]

Crash : https://raw.githubusercontent.com/lcatro/My_PoC/master/swftools/swfc_crash_mem_put_

Trigger : ./swfc swftools/swfc_crash_mem_put_

Crash Detail :

`
fuzzer@ub16x64:~/fuzzing/swftools/src$ ./swfc swftools/swfc_crash_mem_put_

==18776==ERROR: AddressSanitizer: negative-size-param: (size=-1)
#0 0x7f4914cd39a1 in _asan_memcpy (/usr/lib/x86_64-linux-gnu/libasan.so.2+0x8c9a1)
#1 0x487d52 in mem_put (/home/fuzzer/fuzzing/swftools/src/swfc+0x487d52)
#2 0x488202 in mem_putstring (/home/fuzzer/fuzzing/swftools/src/swfc+0x488202)
#3 0x402f59 in store (/home/fuzzer/fuzzing/swftools/src/swfc+0x402f59)
#4 0x4042ed in yylex (/home/fuzzer/fuzzing/swftools/src/swfc+0x4042ed)
#5 0x404f8a in generateTokens (/home/fuzzer/fuzzing/swftools/src/swfc+0x404f8a)
#6 0x411194 in main (/home/fuzzer/fuzzing/swftools/src/swfc+0x411194)
#7 0x7f491412282f in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x2082f)
#8 0x402a08 in _start (/home/fuzzer/fuzzing/swftools/src/swfc+0x402a08)

0x629000005201 is located 1 bytes inside of 16386-byte region [0x629000005200,0x629000009202)
allocated by thread T0 here:
#0 0x7f4914cdf602 in malloc (/usr/lib/x86_64-linux-gnu/libasan.so.2+0x98602)
#1 0x403247 in yyalloc (/home/fuzzer/fuzzing/swftools/src/swfc+0x403247)

SUMMARY: AddressSanitizer: negative-size-param ??:0 __asan_memcpy
==18776==ABORTING
`