Handle with the nonnull case in a tricky way

The func readdir() is not allowed to pass a nullptr.
Bug: b/245972273
Test: mm

Change-Id: Idbb3f552b026dc6d727886d22989d3359ed6633b
diff --git a/debuggerd/crasher/crasher.cpp b/debuggerd/crasher/crasher.cpp
index 4043a6e..6a19878 100644
--- a/debuggerd/crasher/crasher.cpp
+++ b/debuggerd/crasher/crasher.cpp
@@ -164,7 +164,8 @@
 }
 
 noinline void readdir_null() {
-    readdir(nullptr);
+    DIR* sneaky_null = nullptr;
+    readdir(sneaky_null);
 }
 
 noinline int strlen_null() {