Fixes https://bugs.llvm.org/show_bug.cgi?id=48882.
If the input file does not exist (or has a reading error), the
following code will crash if there are two or more input addresses.
```
auto ResOrErr = Symbolizer.symbolizeInlinedCode(
ModuleName, {Offset, object::SectionedAddress::UndefSection});
Printer << (error(ResOrErr) ? DILineInfo() : ResOrErr.get().getFrame(0));
```
For the first address, `symbolizeInlinedCode` returns an error.
For the second address, `symbolizeInlinedCode` returns an empty result
(not an error) and `.getFrame(0)` will crash.
Differential revision: https://reviews.llvm.org/D95609
