audiobuffer: cleanup, make zero-padding explicit

Rationale: it's more obvious that trailing zeroes are being added
here than if no parameter is given.

Refs #49181

Change-Id: Ie7843328e248ac0e195da9c2d62f6b8a9467deaf

daemon/src/audio/audiobuffer.cpp

@@ -129,8 +129,9 @@ void AudioBuffer::resize(size_t sample_num)
     if (frames() == sample_num)
         return;
 
-    for (unsigned i = 0; i < samples_.size(); i++)
-        samples_[i].resize(sample_num);
+    // will add zero padding if buffer is growing
+    for (auto &s : samples_)
+        s.resize(sample_num, 0);
 }
 
 std::vector<SFLAudioSample> * AudioBuffer::getChannel(unsigned chan /* = 0 */)