Fix null-deref in parse_cond_value (#12294)

Summary:


Fuzzer mutates .pte files and expects the loader/executor to handle corrupted input robustly. The crash was due to ***cond_val***. returning nullptr (invalid/corrupted input).
Fix the crash by checking for nullptr and returning an error code.
Now, the fuzzer test case also required to be modified to handle the new returned error code. (The intent of a fuzzing test is to ensure the code does not crash or misbehave on malformed input, not that it always succeeds.)

Reviewed By: JacobSzwejbka

Differential Revision: D77827830

Author: psiddh

runtime/executor/method.cpp

@@ -271,6 +271,8 @@ Result<bool> parse_cond_value(const EValue& cond_value) {
         static_cast<int8_t>(cond_val.scalar_type()));
 
     const bool* cond_data = cond_val.const_data_ptr<bool>();
+    ET_CHECK_OR_RETURN_ERROR(
+        cond_data != nullptr, InvalidState, "Tensor data is null");
     for (size_t i = 0; i < static_cast<size_t>(cond_val.numel()); i++) {
       if (!cond_data[i]) {
         return false;