audio: fix tone creation on iOS

Add value initialization for tones array, otherwise in iOS
behaviour will be undefined.

Change-Id: I604beda02fc4cdc2e6ade94088fdbc2f7d0b9c25

src/media/audio/sound/tonelist.h

@@ -60,7 +60,7 @@ private:
     void buildTones(unsigned int sampleRate);
 
     CountryId countryId_;
-    std::array<std::shared_ptr<Tone>, (size_t) Tone::ToneId::TONE_NULL> tones_;
+    std::array<std::shared_ptr<Tone>, (size_t) Tone::ToneId::TONE_NULL> tones_ {};
     Tone::ToneId currentTone_;
 };