Fix occurrences of const typed declaration without initialization

This fixes compilation errors as the following:

error: constructor must explicitly initialize the const member

BUG=506663
R=aluebs@webrtc.org, tommi@webrtc.org

Signed-off-by: Eduardo Lima (Etrunko) <eduardo.lima@intel.com>

Review URL: https://codereview.webrtc.org/1222233002

Cr-Commit-Position: refs/heads/master@{#9538}

webrtc/modules/audio_processing/include/audio_processing.h

@@ -103,7 +103,9 @@ struct ExperimentalNs {
 // Use to enable beamforming. Must be provided through the constructor. It will
 // have no impact if used with AudioProcessing::SetExtraOptions().
 struct Beamforming {
-  Beamforming() : enabled(false) {}
+  Beamforming()
+      : enabled(false),
+        array_geometry() {}
   Beamforming(bool enabled, const std::vector<Point>& array_geometry)
       : enabled(enabled),
         array_geometry(array_geometry) {}