If `MM->getOwningModule` returns nullptr, then `isVisible` is called
with nullptr, which then calls `getImportLoc(nullptr)`
077e0c134a/clang/lib/Lex/PPMacroExpansion.cpp (L208)
If `MM->getOwningModule` returns nullptr, then `isVisible` is called
with nullptr, which then calls `getImportLoc(nullptr)`
077e0c134a/clang/lib/Lex/PPMacroExpansion.cpp (L208)