[mlir][AsmPrinter] Gracefully handle empty symbol

[boschmitt]

Summary

The GenericOp printer should support malformed IR without crashing

GitHub issue #59529

[rriddle]

mlir/lib/IR/AsmPrinter.cpp

2046

[boschmitt]

Don't change header includes. Add missing '@'

[boschmitt]

@rriddle, I forgot to mention (my apologies) that I don't have commit access, so I need help pushing the patch.

mlir/lib/IR/AsmPrinter.cpp

 //===- AsmPrinter.cpp - MLIR Assembly Printer Implementation --------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
static void printKeywordOrString(StringRef keyword, raw_ostream &os) {
   printEscapedString(keyword, os);
   os << '"';
 }
 
 /// Print the given string as a symbol reference. A symbol reference is
 /// represented as a string prefixed with '@'. The reference is surrounded with
 /// ""'s and escaped if it has any special or non-printable characters in it.
 static void printSymbolReference(StringRef symbolRef, raw_ostream &os) {
-  assert(!symbolRef.empty() && "expected valid symbol reference");
+  if (symbolRef.empty()) {
+    os << "@<<INVALID EMPTY SYMBOL>>";
+    return;
+  }
   os << '@';
   printKeywordOrString(symbolRef, os);
 }
 
 // Print out a valid ElementsAttr that is succinct and can represent any
 // potential shape/type, for use when eliding a large ElementsAttr.
 //
 // We choose to use a dense resource ElementsAttr literal with conspicuous