Schema not applied correctly in library when using library.with_data_values().

**What steps did you take and what happened:**

Run:

```
#!/bin/sh

set -x

mkdir -p resources-1/_ytt_lib/mylib

cat > resources-1/_ytt_lib/mylib/00-schema.yaml << EOF
#@data/values-schema
---
apiVersion: ""
kind: ""
#@schema/type any=True
metadata:
name: ""
uid: ""
#@schema/type any=True
spec: null
#@schema/type any=True
status: null
EOF

cat > resources-1/_ytt_lib/mylib/99-output.yaml << EOF
#@ load("@ytt:data", "data")
--- #@ data.values
EOF

cat > resources-1/99-output.yaml << EOF
#@ load("@ytt:data", "data")
#@ load("@ytt:struct", "struct")
#@ load("@ytt:library", "library")
#@ load("@ytt:template", "template")

#@ mylib = library.get("mylib")
#@ mylib_with_values = mylib.with_data_values(struct.decode(data.values))

--- #@ template.replace(mylib_with_values.eval())
EOF

cat > values-1.yaml << EOF
apiVersion: v1
kind: Namespace
metadata:
creationTimestamp: "2021-10-13T05:54:35Z"
labels:
kubernetes.io/metadata.name: default
name: default
resourceVersion: "201"
uid: 591eeb77-5c81-49de-8698-28ac704d0467
spec:
finalizers:
- kubernetes
status:
phase: Active
EOF

ytt -f resources-1 --data-values-file values-1.yaml
```

This results in the error:

```
ytt: Error:
- library.eval: Evaluating library 'mylib': Overlaying data values (in following order: additional data values): Document on line ?: Map item (key 'metadata') on line ?: Map item (key 'creationTimestamp') on line ?: Expected number of matched nodes to be 1, but was 0
in
99-output.yaml:9 | --- #@ template.replace(mylib_with_values.eval())
```

With the files created from the test, if you were instead to run:

```
ytt -f resources-1/_ytt_lib/mylib --data-values-file values-1.yaml
```

In other words, directly process the files which are in the library, it works fine and produces:

```
apiVersion: v1
kind: Namespace
metadata:
name: default
uid: 591eeb77-5c81-49de-8698-28ac704d0467
creationTimestamp: "2021-10-13T05:54:35Z"
labels:
kubernetes.io/metadata.name: default
resourceVersion: "201"
spec:
finalizers:
- kubernetes
status:
phase: Active
```

Note that there is no `#@data/values` file in the library.

Now run a second test where the only difference is that we add a `#@data/values` file to the library, but where it is only marked as such and has no actual values set:

```
#!/bin/sh

set -x

mkdir -p resources-2/_ytt_lib/mylib

cat > resources-2/_ytt_lib/mylib/00-schema.yaml << EOF
#@data/values-schema
---
apiVersion: ""
kind: ""
#@schema/type any=True
metadata:
name: ""
uid: ""
#@schema/type any=True
spec: null
#@schema/type any=True
status: null
EOF

cat > resources-2/_ytt_lib/mylib/00-values.yaml << EOF
#@data/values
---
EOF

cat > resources-2/_ytt_lib/mylib/99-output.yaml << EOF
#@ load("@ytt:data", "data")
--- #@ data.values
EOF

cat > resources-2/99-output.yaml << EOF
#@ load("@ytt:data", "data")
#@ load("@ytt:struct", "struct")
#@ load("@ytt:library", "library")
#@ load("@ytt:template", "template")

#@ mylib = library.get("mylib")
#@ mylib_with_values = mylib.with_data_values(struct.decode(data.values))

--- #@ template.replace(mylib_with_values.eval())
EOF

cat > values-2.yaml << EOF
apiVersion: v1
kind: Namespace
metadata:
creationTimestamp: "2021-10-13T05:54:35Z"
labels:
kubernetes.io/metadata.name: default
name: default
resourceVersion: "201"
uid: 591eeb77-5c81-49de-8698-28ac704d0467
spec:
finalizers:
- kubernetes
status:
phase: Active
EOF

ytt -f resources-2 --data-values-file values-2.yaml
```

This time the test works and we get same output as when had processed the files in the library directly.

So in order for `library.with_data_values()` to work, you need to have a `#@data/values` file present.

Be warned though, that the data values file cannot actually have any values set in it, or you get an error again as seen with test:

```
#!/bin/sh

set -x

mkdir -p resources-3/_ytt_lib/mylib

cat > resources-3/_ytt_lib/mylib/00-schema.yaml << EOF
#@data/values-schema
---
apiVersion: ""
kind: ""
#@schema/type any=True
metadata:
name: ""
uid: ""
#@schema/type any=True
spec: null
#@schema/type any=True
status: null
EOF

cat > resources-3/_ytt_lib/mylib/00-values.yaml << EOF
#@data/values
---
metadata:
name: "xxx"
EOF

cat > resources-3/_ytt_lib/mylib/99-output.yaml << EOF
#@ load("@ytt:data", "data")
--- #@ data.values
EOF

cat > resources-3/99-output.yaml << EOF
#@ load("@ytt:data", "data")
#@ load("@ytt:struct", "struct")
#@ load("@ytt:library", "library")
#@ load("@ytt:template", "template")

#@ mylib = library.get("mylib")
#@ mylib_with_values = mylib.with_data_values(struct.decode(data.values))

--- #@ template.replace(mylib_with_values.eval())
EOF

cat > values-3.yaml << EOF
apiVersion: v1
kind: Namespace
metadata:
creationTimestamp: "2021-10-13T05:54:35Z"
labels:
kubernetes.io/metadata.name: default
name: default
resourceVersion: "201"
uid: 591eeb77-5c81-49de-8698-28ac704d0467
spec:
finalizers:
- kubernetes
status:
phase: Active
EOF

ytt -f resources-3 --data-values-file values-3.yaml
```

Which again generates the error:

```
ytt: Error:
- library.eval: Evaluating library 'mylib': Overlaying data values (in following order: _ytt_lib/mylib/00-values.yaml, additional data values): Document on line ?: Map item (key 'metadata') on line ?: Map item (key 'creationTimestamp') on line ?: Expected number of matched nodes to be 1, but was 0
in
99-output.yaml:9 | --- #@ template.replace(mylib_with_values.eval())
```

**What did you expect:**

Expect the following:

* It should not be required to have an empty `#@data/values` annotated file to get it to work.
* Where the `#@data/values` file sets values it should not error and the values passed to `library.with_data_values()` should me merged just like if `--data-values-file` was used on the command line and it was overriding a data values file included with a set of YAML files where a library wasn't involved.

**Environment:**

```
% ytt version
ytt version 0.38.0
```

---
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