chore: fix bad error message on insert into

[agavra]

Description

fixes #6760 by ensuring that the old error message is thrown when we try to insert into a source with more columns than it has. before this patch, the code would fail with IndexOutOfBounds exception when trying to get the column at an index greater than the number of columns. this fixes it by "ignoring" that column and just letting it throw later down the line.

Testing done

QTT testing

Reviewer checklist

• Ensure docs are updated if necessary. (eg. if a user visible feature is being added or changed).
• Ensure relevant issues are linked (description should include text like "Fixes #")

[spena]

LGTM for a quick fix. However I think we'll need to change the error message in the future. If either the target or resulted schema are too wide and include many complex types (say 30 columns + several nested struct columns), then the error will be huge.

I don't have a message proposal, but I feel we'll need to change it later.

[agavra]

Makes sense @spena - I had thought about this too but didn't come up with a great suggestion.