community[patch]: helpful error message for GitHubAPIWrapper (#14803)

Very simple change in relation to the issue
https://github.com/langchain-ai/langchain/issues/14550

@baskaryan, @eyurtsev, @hwchase17.

---------

Co-authored-by: Harrison Chase <hw.chase.17@gmail.com>
Co-authored-by: Bagatur <baskaryan@gmail.com>

libs/community/langchain_community/utilities/github.py

@@ -76,8 +76,16 @@ class GitHubAPIWrapper(BaseModel):
             private_key,
         )
         gi = GithubIntegration(auth=auth)
-        installation = gi.get_installations()[0]
-
+        installation = gi.get_installations()
+        if not installation:
+            raise ValueError(
+                f"Please make sure to install the created github app with id "
+                f"{github_app_id} on the repo: {github_repository}"
+                "More instructions can be found at "
+                "https://docs.github.com/en/apps/using-"
+                "github-apps/installing-your-own-github-app"
+            )
+        installation = installation[0]
         # create a GitHub instance:
         g = installation.get_github_for_installation()
         repo = g.get_repo(github_repository)