[scudo] Fix stack depot validation. (#87024)

In the StackDepot::isValid function, there is work to validate the
TabMask variable. Unfortunately, if TabMask is set to the maximum
allowed value, TabSize = TabMask + 1 becomes zero and validation passes.

Disallow that case to prevent invalid reads into the Tab structure.

Author: cferris1000

compiler-rt/lib/scudo/standalone/stack_depot.h

@@ -112,7 +112,7 @@ class alignas(atomic_u64) StackDepot {
     if (TabMask == 0)
       return false;
     uptr TabSize = TabMask + 1;
-    if (!isPowerOfTwo(TabSize))
+    if (TabSize == 0 || !isPowerOfTwo(TabSize))
       return false;
     uptr TabBytes = sizeof(atomic_u32) * TabSize;