Fix checking for subdirs when parsing apks

This fixes the check for subdirectories in lib paths. The old check
caused a crash.

Test: Automated
Fixes: 268582810
Change-Id: I520f1fd6772b11821e7c5c97bd51b45b603f5a7b
diff --git a/libs/androidfw/tests/ApkParsing_test.cpp b/libs/androidfw/tests/ApkParsing_test.cpp
index 4aab0a1..62e88c6 100644
--- a/libs/androidfw/tests/ApkParsing_test.cpp
+++ b/libs/androidfw/tests/ApkParsing_test.cpp
@@ -68,4 +68,10 @@
   auto lastSlash = util::ValidLibraryPathLastSlash(path, false, false);
   ASSERT_THAT(lastSlash, IsNull());
 }
+
+TEST(ApkParsingTest, InvalidFileAtRoot) {
+  const char* path = "lib/library.so";
+  auto lastSlash = util::ValidLibraryPathLastSlash(path, false, false);
+  ASSERT_THAT(lastSlash, IsNull());
+}
 }
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