Tone down a fatal assert

The new disconnectDisplay function doesn't handle virtual displays,
but it may be called for them.  Return without doing anything.

Bug 7281786

Change-Id: I62607f2ae6073fa66b393f55932604aeb8e03566
diff --git a/services/surfaceflinger/DisplayHardware/HWComposer.cpp b/services/surfaceflinger/DisplayHardware/HWComposer.cpp
index 597e5d6..dd9a762 100644
--- a/services/surfaceflinger/DisplayHardware/HWComposer.cpp
+++ b/services/surfaceflinger/DisplayHardware/HWComposer.cpp
@@ -686,8 +686,11 @@
 }
 
 void HWComposer::disconnectDisplay(int disp) {
-    LOG_ALWAYS_FATAL_IF(disp < 0 || disp == HWC_DISPLAY_PRIMARY ||
-                        disp >= HWC_NUM_DISPLAY_TYPES);
+    LOG_ALWAYS_FATAL_IF(disp < 0 || disp == HWC_DISPLAY_PRIMARY);
+    if (disp >= HWC_NUM_DISPLAY_TYPES) {
+        // nothing to do for these yet
+        return;
+    }
     DisplayData& dd(mDisplayData[disp]);
     if (dd.list != NULL) {
         free(dd.list);