(Re)allocate and clear the stereo-to-binaural filter as needed

Alc/ALc.c

@@ -1214,14 +1214,21 @@ ALCAPI ALCcontext* ALCAPIENTRY alcCreateContext(ALCdevice *device, const ALCint
 
             ALContext->Frequency = device->Frequency;
 
-            free(device->Bs2b);
-            device->Bs2b = NULL;
             if(device->Bs2bLevel > 0 && device->Bs2bLevel <= 6)
             {
-                device->Bs2b = calloc(1, sizeof(*device->Bs2b));
+                if(!device->Bs2b)
+                {
+                    device->Bs2b = calloc(1, sizeof(*device->Bs2b));
+                    bs2b_clear(device->Bs2b);
+                }
                 bs2b_set_srate(device->Bs2b, device->Frequency);
                 bs2b_set_level(device->Bs2b, device->Bs2bLevel);
             }
+            else
+            {
+                free(device->Bs2b);
+                device->Bs2b = NULL;
+            }
 
             ProcessContext(NULL);
         }

Alc/bs2b.c

@@ -113,8 +113,6 @@ static void init(struct bs2b *bs2b)
     bs2b->a1_hi = -x;
 
     bs2b->gain  = 1.0 / (1.0 - G_hi + G_lo);
-
-    bs2b_clear(bs2b);
 } /* init */
 
 /* Exported functions.