Error message on missing branch in schedule files

This is an example when we have an undefined branch exists in Case (or input file). An example here the `YO` well is defined as two branches in input file, but the schedule file only defined one branch.

This happens when running uncertainty analysis, one branch is not produced by pre-processor but the user expects it to be produced while making Completor case file.

### **To Reproduce**
Rerun Completor with attached files

### **Expected behavior**
Described below

Start by rerunning Completor with the attached input and schedule files, focusing on the case where the YO well has two input branches but only one schedule branch. Trace how uncertainty analysis handles the branch missing from the pre-processor output. Done means the missing-branch case produces the expected error message described in the issue.

Written by the indexing model from the issue text.