Use wflags to access wtab->flags in LookupDict2.

Clang static analysis reports a 'Dereference of null pointer'
error when accessing wtab->flags. This is properly guarded
against when setting the wflags variable, so use that variable
instead.

src/libespeak-ng/dictionary.c

 			continue;
 		}
 
-		if ((dictionary_flags2 & FLAG_ATSTART) && !(wtab->flags & FLAG_FIRST_WORD)) {
+		if ((dictionary_flags2 & FLAG_ATSTART) && !(wflags & FLAG_FIRST_WORD)) {
 			// only use this pronunciation if it's the first word of a clause
 			continue;
 		}