Some small fixes in SBOM generation

1) Fix column name typo in compliance metadata db
2) Add new identifier type: Piper
3) Add checking in case some static libraries' soong module could not be identified, which happens on some java static libraries

Test: presubmits
Test: build/soong/tests/sbom_test.sh
Change-Id: I2815ddff5f39b5a562668ac19f694461f8a01cd7
diff --git a/tools/sbom/gen_sbom.py b/tools/sbom/gen_sbom.py
index 756d9db..77bccbb 100644
--- a/tools/sbom/gen_sbom.py
+++ b/tools/sbom/gen_sbom.py
@@ -92,6 +92,7 @@
     'SVN',
     'Hg',
     'Darcs',
+    'Piper',
     'VCS',
     'Archive',
     'PrebuiltByAlphabet',
@@ -708,7 +709,10 @@
         'installed_file': dep_file,
         'is_prebuilt_make_module': False
     }
-    file_metadata.update(db.get_soong_module_of_built_file(dep_file))
+    soong_module = db.get_soong_module_of_built_file(dep_file)
+    if not soong_module:
+      continue
+    file_metadata.update(soong_module)
     if is_source_package(file_metadata) or is_prebuilt_package(file_metadata):
       add_package_of_file(file_id, file_metadata, doc, report)
     else: