Collector fails to detect file extension of command correctly on Windows

When checking if the base call of the command has a file extension, Collector incorrectly runs the extname function on the entire command string (cmd) instead of the just the base call (cmd0). As a result, it sometimes thinks that the base call has a file extension when it does not.

Example:

gradlew :my.project.api:generateDocs

In this case, no file extension should be detected.