Invalid textfile collector file brings down whole exporter

[Mario-Hofstaetter]

Certain malformed .prom files are handled gracefully by the exporter
However, there are some cases that will bring down the whole exporter endpoint (HTTP 500) and show an exception.

Example:
Add this as oh-oh.prom to the textfile collector directory:

# HELP windows_sometest This is a Test.
# TYPE windows_sometest gauge
windows_sometest{display_name="foobar",display_version="13.4.0"} 1
windows_sometest{display_name="foobar",display_version="13.4.0"} 1

This brings down the whole exporter:

❯ curl.exe http://localhost:9182/metrics --verbose
HTTP/1.1 500 Internal Server Error
An error has occurred while serving metrics:
collected metric "windows_sometest" { label:<name:"display_name" value:"foobar" > label:<name:"display_version" value:"13.4.0" > gauge:<value:1 > } was collected before with the same name and label values

There are several possible cases, where duplicate/mixed format metrics cause this error. This can happen quite easily when using scripting and textfile collector.

Can this be fixed?

Expected behavior is that windows_textfile_scrape_error returns 1 but other metrics should continue to work.