dictionary: fix stack initialization

src/libespeak-ng/dictionary.c

@@ -927,6 +927,9 @@ void SetWordStress(Translator *tr, char *output, unsigned int *dictionary_flags,
 
 	static const char consonant_types[16] = { 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0 };
 
+	memset(syllable_weight, 0, sizeof(syllable_weight));
+	memset(vowel_length, 0, sizeof(vowel_length));
+
 	stressflags = tr->langopts.stress_flags;
 
 	if (dictionary_flags != NULL)