scripts/logging: Skip log symbols of zero size

I'm not sure why this was necessary, but analyzing RX
executables was crashing with a divide by zero error on a
symbol which appeared to be duplicated in this list.

Signed-off-by: Keith Packard <keithp@keithp.com>

scripts/logging/dictionary/database_gen.py

@@ -206,6 +206,10 @@ def parse_log_const_symbols(database, log_const_area, log_const_symbols, string_
             # Not enough data to unpack
             continue
 
+        if sym.entry['st_size'] == 0:
+            # Empty entry
+            continue
+
         str_ptr, level = struct.unpack(formatter, datum)
 
         # Offset to rodata section for string