Fix a rewriter bug by disabling the rewriter in a special case.

I encountered this issue sometimes with the protobuf integration test.

src/asm_writing/rewriter.cpp

@@ -970,10 +970,12 @@ void Rewriter::_call(RewriterVar* result, bool has_side_effects, void* func_addr
         assert(assembler->hasFailed() || asm_address == (uint64_t)assembler->curInstPointer());
     }
 
+    if (!failed) {
         assert(vars_by_location.count(assembler::RAX) == 0);
         result->initializeInReg(assembler::RAX);
 
         assertConsistent();
+    }
 
     result->releaseIfNoUses();
 }

src/runtime/types.cpp

@@ -932,6 +932,8 @@ static Box* typeCallInner(CallRewriteArgs* rewrite_args, ArgPassSpec argspec, Bo
                 rewrite_args->rewriter->call(true, (void*)assertInitNone, srewrite_args.out_rtn);
             }
         } else {
+            rewrite_args = NULL;
+
             init_attr = processDescriptor(init_attr, made, cls);
 
             ArgPassSpec init_argspec = argspec;