Properly handle the case when .symtab does not exist in a file

* bdx/binary.py (_read_symbols_in_file): Return no symbols if the
symbol table does not exist, in order to prevent the file from being
always treated as unindexed.

Author: mkcms

bdx/binary.py

@@ -22,7 +22,7 @@
 from elftools.elf.sections import SymbolTableSection
 from sortedcontainers import SortedList
 
-from bdx import debug, info, make_progress_bar, trace
+from bdx import debug, info, log, make_progress_bar, trace
 
 
 class NameDemangler:
@@ -313,6 +313,9 @@ def _read_symbols_in_file(
     use_dwarfdump: bool,
 ) -> list[Symbol]:
     symtab = elf.get_section_by_name(".symtab")
+    if symtab is None:
+        log("warning: {}: .symtab section does not exist", file, symtab)
+        return []
     if not isinstance(symtab, SymbolTableSection):
         msg = ".symtab is not a SymbolTableSection"
         raise RuntimeError(msg)