Omit bazel.LabelList attrs if no path is specified

Test: go test build_conversion_test.go
Change-Id: Ibcd81049788e99422569fe74e5f3834df4a05122

android/paths.go

@@ -395,6 +395,9 @@ func BazelLabelForModuleSrcExcludes(ctx BazelConversionPathContext, paths, exclu
 // `android:"path"` so that dependencies on other modules will have already been handled by the
 // path_properties mutator.
 func expandSrcsForBazel(ctx BazelConversionPathContext, paths, expandedExcludes []string) bazel.LabelList {
+	if paths == nil {
+		return bazel.LabelList{}
+	}
 	labels := bazel.LabelList{
 		Includes: []bazel.Label{},
 	}

bp2build/build_conversion_test.go

@@ -468,6 +468,21 @@ genrule {
 		fs                                 map[string]string
 		dir                                string
 	}{
+		{
+			description:                        "filegroup with does not specify srcs",
+			moduleTypeUnderTest:                "filegroup",
+			moduleTypeUnderTestFactory:         android.FileGroupFactory,
+			moduleTypeUnderTestBp2BuildMutator: android.FilegroupBp2Build,
+			bp: `filegroup {
+    name: "fg_foo",
+    bazel_module: { bp2build_available: true },
+}`,
+			expectedBazelTargets: []string{
+				`filegroup(
+    name = "fg_foo",
+)`,
+			},
+		},
 		{
 			description:                        "filegroup with no srcs",
 			moduleTypeUnderTest:                "filegroup",