imageInputStream is null, giving file size of .LBL instead of .IMG

[jordanpadams]

Describe the bug
When running generate on a .LBL file in debug mode, from FileSize.java see this line:

Debugger.debug("file="+this.file+" imageInputStream="+this.imageInputStream);

(see internal ticket for exact location)

that the imageInputStream is null. This results in $generate.file_size returning the size of the .LBL file instead of its corresponding .IMG file.

To Reproduce
Steps to reproduce the behavior:

1. Go to https://github.jpl.nasa.gov/PDSIMG/pdsimg-mi
2. Clone the repo
3. Checkout branch nsyt-ida
4. Install generate 0.15.0 or 0.18.2
5. From the repo root, run

generate -d -t schemas/juno/sample_products/juno_jnc_template.xml -p schemas/juno/sample_products/JNCE_2011238_00A00002_V01.LBL

Expected behavior
It is expected that the imageInputStream not be null so that the file size of the .IMG file be returned.

Version of Software Used
0.15.0 and 0.18.2

Screenshots
See internal ticket

Desktop (please complete the following information):

• OS: macOS 10.14.6 Mojave

@decesare