Align_mosaics issue

[catherine-martlin]

Appears a couple help tickets have reported an issue with step 6 in align_mosaics. The error ends in: KeyError: "Extension ('', 1) not found."

Suggested method to fix this is to update step 5a to have build=True as this will create a drizzle file with the science and weight extension in one and have that be the reference image in step 6. This will also need an update to the plotting in 5b.