Fix crash while editing asm.

[karliss]

Empty input field resulted in empty byteArray and constData pointing to null, which rz_hex_bin2str didn't expect.

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Detailed description

Thanks @ravenexp for testing and debugging the problem.

Not only the function didn't handle empty QByteArray, there was a second hidden problem. The function reserved memory for 2n bytes but rz_hex_bin2str writes a null terminated string thus requiring 2n+1 bytes of space. The extra null byte write was probably also what caused the crash, just for non empty arrays single byte buffer overflow would most of the time not cause easily observable sideeffects.

Test plan (required)

1. open executable
2. enable cache mode
3. in disasm widget edit instruction
   • change constant -> observe that there are no errors and byte preview updates
   • delete all text -> should not crash
   • write a different valid instruction for example nop -> bytes should be updated

Closing issues

Closes #3374, closes #3356

[Rot127]

The rz_hex_str2bin function needs some work tbh. But it does so much more then it says (you can have comments in the string!), that it is scary to touch it

[karliss]

The rz_hex_str2bin function needs some work tbh. But it does so much more then it says (you can have comments in the string!), that it is scary to touch it

For a moment you got me scared, but in this case it was bin2str not not str2bin.