Avoid division by 0 when parsing WAV data

Don't divide by waveformat.uiBlockAlign which could be 0, but rather
multiply by it and verify that we get the expected result. This is more
robust, as it prevents crashes on malformed input and also slightly more
efficient even for correct input.

src/unix/sound.cpp

@@ -669,8 +669,8 @@ bool wxSound::LoadWAV(const void* data_, size_t length, bool copyData)
     if (waveformat.uiFormatTag != WAVE_FORMAT_PCM)
         return false;
 
-    if (waveformat.ulSamplesPerSec !=
-        waveformat.ulAvgBytesPerSec / waveformat.uiBlockAlign)
+    if (waveformat.ulAvgBytesPerSec !=
+        waveformat.ulSamplesPerSec * waveformat.uiBlockAlign)
         return false;
 
     // get file size from header