[llvm-readobj] Fix UB in pointer arithmetics after D105522

Author: vitalybuka

llvm/tools/llvm-readobj/ObjDumper.cpp

@@ -54,6 +54,8 @@ static void printAsPrintable(raw_ostream &W, const uint8_t *Start, size_t Len) {
 
 void ObjDumper::printAsStringList(StringRef StringContent,
                                   size_t StringDataOffset) {
+  if (StringContent.size() < StringDataOffset)
+    return;
   const uint8_t *StrContent = StringContent.bytes_begin();
   // Some formats contain additional metadata at the start which should not be
   // interpreted as strings. Skip these bytes, but account for them in the