FdSizeReport: Handle empty FV sections in Build Report (#664)

## Description

Updates the FdSizeReportGenerator to handle the scenario where the build
report contains an empty FD region.

This scenario was not previously seen but has been verified and has been
noted to happen when a nested FV does not contain any modules. In this
scenario, the "Size: " line is not present and there is no subsection
table where the included files would normally be present.

Example of empty FD region:
```
>----------------------------------------------------------------------------------------------------------------------<
Nested FV
Type:               FV
Base Address:       0x0
<---------------------------------------------------------------------------------------------------------------------->
``` 

- [ ] Impacts functionality?
- **Functionality** - Does the change ultimately impact how firmware
functions?
- Examples: Add a new library, publish a new PPI, update an algorithm,
...
- [ ] Impacts security?
- **Security** - Does the change have a direct security impact on an
application,
    flow, or firmware?
  - Examples: Crypto algorithm change, buffer overflow fix, parameter
    validation improvement, ...
- [ ] Breaking change?
- **Breaking change** - Will anyone consuming this change experience a
break
    in build or boot behavior?
- Examples: Add a new library class, move a module to a different repo,
call
    a function in a new library class in a pre-existing module, ...
- [ ] Includes tests?
  - **Tests** - Does the change include any explicit test code?
  - Examples: Unit tests, integration tests, robot tests, ...
- [ ] Includes documentation?
- **Documentation** - Does the change contain explicit documentation
additions
    outside direct code modifications (and comments)?
- Examples: Update readme file, add feature readme file, link to
documentation
    on an a separate Web page, ...

## How This Was Tested

Reproduced error on partner platform and verified changes resolved the
issue.

## Integration Instructions

N/A

BaseTools/Plugin/FdSizeReport/FdSizeReportGenerator.py

@@ -188,6 +188,7 @@ class FdRegion:
         as we can pseudo treat it like a factory class.
     """
     FD_REGION = r"Type:\s+(.*?)(?:\r?\n|\r)Base Address:\s+(.*?)(?:\r?\n|\r)Size:\s+(.*?)(?:\r?\n|\r)"
+    FD_EMPTY_REGION = r"Type:\s+(.*?)(?:\r?\n|\r)Base Address:\s+(.*?)(?:\r?\n|\r)"
 
     TYPE_FV = r"Fv Name:\s+(.*?)(?:\r?\n|\r)Occupied Size:\s+(.*?)(?:\r?\n|\r)Free Size:\s+(.*?)(?:\r?\n|\r)"
     TYPE_CAPSULE = r"Capsule Name:\s+(.*?)(?:\r?\n|\r)?Capsule Size:\s+(.*?)"
@@ -257,7 +258,7 @@ def parse_capsule_file_type_region(match: re.Match) -> 'FdRegion':
         # "Capsule Size:" or "File Size:", `0x348000 (3360K)` -> `0x348000`
         region.size = match.group(5).strip().split()[0]
 
-    def parse_generic_region(match: re.match) -> 'FdRegion':
+    def parse_generic_region(match: re.match, empty: bool) -> 'FdRegion':
         """Parses a generic FD region header.
 
         Args:
@@ -269,7 +270,8 @@ def parse_generic_region(match: re.match) -> 'FdRegion':
         region.base = match.group(2).strip()
 
         # `0x348000 (3360K)` -> `0x348000`
-        region.size = match.group(3).strip().split()[0]
+        if not empty:
+            region.size = match.group(3).strip().split()[0]
         return region
 
     def from_raw(raw_region: str, nested):
@@ -303,7 +305,12 @@ def from_raw(raw_region: str, nested):
         match = re.search(FdRegion.FD_REGION, raw_region, re.DOTALL)
         if match:
             logging.debug("Generic FD Region found.")
-            return FdRegion.parse_generic_region(match)
+            return FdRegion.parse_generic_region(match, False)
+
+        match = re.search(FdRegion.FD_EMPTY_REGION, raw_region, re.DOTALL)
+        if match:
+            logging.debug("Empty FD Region found.")
+            return FdRegion.parse_generic_region(match, True)
 
         logging.error("No match found for FD Region")
         return None