app_server: Catch drawing (AGG) allocation exceptions.

Since _DispatchViewDrawingMessage sends single B_ERROR replies
in a number of generic cases, doing so here is probably fine;
it's much better than crashing, anyway.

This is the generalized case of PulkoMandy's earlier patch,
which only applied to one drawing operation. This now affects
all AGG calls.

Change-Id: I751439e43cc300b964ac4cf41c48c1df30baf0a3
Reviewed-on: https://review.haiku-os.org/c/haiku/+/1863
Reviewed-by: Stephan Aßmus <superstippi@gmx.de>

src/servers/app/ServerWindow.cpp

@@ -2451,7 +2451,21 @@ fDesktop->LockSingleWindow();
 		}
 
 		default:
-			_DispatchViewDrawingMessage(code, link);
+			// The drawing code handles allocation failures using exceptions;
+			// so we need to account for that here.
+			try {
+				_DispatchViewDrawingMessage(code, link);
+			} catch (std::bad_alloc&) {
+				// Cancel any message we were in the middle of sending.
+				fLink.CancelMessage();
+
+				if (link.NeedsReply()) {
+					// As done in _DispatchViewDrawingMessage, send just a
+					// single status_t as the reply.
+					fLink.StartMessage(B_NO_MEMORY);
+					fLink.Flush();
+				}
+			}
 			break;
 	}
 }