feat: report errors in macro definition

Reporting macro *definition* error at the macro *call site* is a rather
questionable approach, but at least we don't erase the errors
altogether!

crates/hir_expand/src/lib.rs

@@ -143,7 +143,7 @@ impl HirFileId {
                     _ => None,
                 });
 
-                let macro_def = db.macro_def(loc.def)?;
+                let macro_def = db.macro_def(loc.def).ok()?;
                 let (parse, exp_map) = db.parse_macro_expansion(macro_file).value?;
                 let macro_arg = db.macro_arg(macro_file.macro_call_id)?;