Add fix for specifying current dir in collections_paths (#62478)

(cherry picked from commit 2e1c6a7839)

changelogs/fragments/collection-prefix-basedir.yaml

@@ -0,0 +1,2 @@
+bugfixes:
+- Fix issue where the collection loader tracebacks if ``collections_paths = ./`` is set in the config

lib/ansible/utils/collection_loader.py

@@ -519,7 +519,7 @@ def get_collection_name_from_path(path):
             # strip off the common prefix (handle weird testing cases of nested collection roots, eg)
             collection_remnant = n_path[len(coll_path):]
             # commonprefix may include the trailing /, prepend to the remnant if necessary (eg trailing / on root)
-            if collection_remnant[0] != '/':
+            if collection_remnant and collection_remnant[0] != '/':
                 collection_remnant = '/' + collection_remnant
             # the path lives under this collection root, see if it maps to a collection
             found_collection = _N_COLLECTION_PATH_RE.search(collection_remnant)