tool_cb_prg: Fix integer overflow in progress bar

[danielgustafsson]

Commit 61faa0b fixed the progress bar width calculation to avoid integer overflow, but failed to account for the fact that initial_size is initialized to -1 causing another signed integer overflow. Fix by separately checking for this case before the width calculation.

Closes #xxxx
Reported-by: Brian Carpenter (Geeknik Labs)

[bagder]

Maybe add a comment on why/how it can be less than zero at this point?

[jay]

Maybe add a comment on why/how it can be less than zero at this point?

AFAICT it's only set to -1 to signal resuming an upload and that only works with FTP (and SSH) where libcurl gets the file size of the remote file and then resumes the upload from that position.

curl/src/tool_operate.c

Lines 747 to 748 in 69248b5

	if(uploadfile && config->resume_from_current)
	config->resume_from = -1; /* -1 will then force get-it-yourself */