[wasm] Handle potentially null callee-pc

src/frames.h

Index: src/frames.h
diff --git a/src/frames.h b/src/frames.h
index 06703dd52cfc2a95788c82b4839d8aa138c7f23e..1114576374c05065550b1a9370fe152f02250d66 100644
--- a/src/frames.h
+++ b/src/frames.h
@@ -484,7 +484,9 @@ class StackFrame BASE_EMBEDDED {
   // Accessors.
   Address sp() const { return state_.sp; }
   Address fp() const { return state_.fp; }
-  Address callee_pc() const { return *state_.callee_pc_address; }
+  Address callee_pc() const {
+    return state_.callee_pc_address ? *state_.callee_pc_address : nullptr;
+  }
   Address caller_sp() const { return GetCallerStackPointer(); }
 
   // If this frame is optimized and was dynamically aligned return its old