fix codegen to not segfault if compile failed

src/ngraph/codegen/compiler.cpp

@@ -193,14 +193,15 @@ std::unique_ptr<llvm::Module> execution_state::compile(const string& source, con
 
     // Create and execute action
     CodeGenAction* compilerAction = new EmitCodeGenOnlyAction();
-    if (Clang->ExecuteAction(*compilerAction) == false)
+    std::unique_ptr<llvm::Module> rc;
+    if (Clang->ExecuteAction(*compilerAction) == true)
     {
-        throw runtime_error("codegen compile failed");
+        rc = compilerAction->takeModule();
     }
 
     buffer.release();
 
-    return compilerAction->takeModule();
+    return rc;
 }
 
 bool execution_state::add_module(std::unique_ptr<llvm::Module>& module)

src/ngraph/runtime/cpu/external_function.cpp

@@ -371,7 +371,10 @@ extern "C" void free_aligned_buffer(void* allocated);
 #endif
 
     auto llvm_module = estate.compile(code, "__ngcpu_codegen.cpp");
-    assert(llvm_module);
+    if (llvm_module == nullptr)
+    {
+        throw runtime_error("function failed to compile");
+    }
     estate.add_module(llvm_module);
     estate.finalize();
     m_compiled_function = estate.find_function<EntryPoint_t>(function_name);