Play iPhone audio through default speaker when no devices connected

When no devices are connected, play audio through the default audio
playback speakers (for iPhone 6, 7, 8 these are located at the bottom of
the handset) rather than through the earpiece speaker, which is designed
for taking calls and is much quieter.

Author: Robin Smith

src/ios/RmxAudioPlayer.m

@@ -45,7 +45,7 @@ - (void) pluginInitialize
     _isReplacingItems = NO;
     _isWaitingToStartPlayback = NO;
     self.rate = 1.0f;
-    self.volume = 1f;
+    self.volume = 1.0f;
     self.loop = false;
 
     [self activateAudioSession];
@@ -1284,6 +1284,9 @@ - (void) activateAudioSession
         options |= AVAudioSessionCategoryOptionAllowBluetoothA2DP;
     }
 
+    // If no devices are connected, play audio through the default speaker (rather than the earpiece)
+    options |= AVAudioSessionCategoryOptionDefaultToSpeaker;
+
     [avSession setCategory:AVAudioSessionCategoryPlayAndRecord withOptions:options error:&categoryError];
     if (categoryError) {
         NSLog(@"Error setting category! %@", [categoryError description]);