mixer/Volume: remove logging (mostly useless)

src/mixer/Volume.cxx

@@ -21,10 +21,8 @@
 #include "output/MultipleOutputs.hxx"
 #include "Idle.hxx"
 #include "util/StringCompare.hxx"
-#include "util/Domain.hxx"
 #include "system/PeriodClock.hxx"
 #include "io/BufferedOutputStream.hxx"
-#include "Log.hxx"
 
 #include <cassert>
 
@@ -32,8 +30,6 @@
 
 #define SW_VOLUME_STATE                         "sw_volume: "
 
-static constexpr Domain volume_domain("volume");
-
 static unsigned volume_software_set = 100;
 
 /** the cached hardware mixer value; invalid if negative */
@@ -105,9 +101,7 @@ read_sw_volume_state(const char *line, MultipleOutputs &outputs)
 	sv = strtol(line, &end, 10);
 	if (*end == 0 && sv >= 0 && sv <= 100)
 		software_volume_change(outputs, sv);
-	else
-		FmtWarning(volume_domain,
-			   "Can't parse software volume: {}", line);
+
 	return true;
 }