Fix split category update

* Before there was a CategoryButton that would insert a category in the
  CategoryBox, there was only the CategoryBox' AutoTextControl() that
  did autocomplete and informed the SplitView that the category was
  edited.

  The CategoryButton simply inserting the new category in the text control
  isn't enough. It has to notify the SplitView of that, so it can update
  a changed category in the the list of split transactions at the bottom
  of the window.

  After introducing GetMessenger() to the AutoTextControlFilter we can now
  send a M_SPLIT_CATEGORY_CHANGED to the CategoryBox's parent, i.e. the
  SplitView.

* Split transactions get the category "Split transaction" by the app.
  Ignore those when checking against existing user-created categories.
  It won't be found there and would get added as new user-created category.

src/AutoTextControl.cpp

@@ -199,3 +199,9 @@ AutoTextControlFilter::SetMessenger(BMessenger* msgr)
 		delete fMessenger;
 	fMessenger = msgr;
 }
+
+BMessenger*
+AutoTextControlFilter::GetMessenger()
+{
+	return fMessenger;
+}

src/AutoTextControl.h

@@ -74,6 +74,7 @@ class AutoTextControlFilter : public BMessageFilter {
 
 	void SendMessage(BMessage* msg);
 	void SetMessenger(BMessenger* msgr);
+	BMessenger* GetMessenger();
 
 private:
 	AutoTextControl* fBox;

src/CategoryBox.cpp

@@ -140,7 +140,8 @@ CategoryBox::SetTypeFromCategory(BString category)
 	}
 
 	bool success = true;
-	if (!categoryExists)
+	if (!categoryExists
+		&& category.ICompare(B_TRANSLATE_CONTEXT("Split transaction", "CommonTerms")) != 0)
 		bool success = AddNewCategory(category);
 
 	return success;

src/CategoryButton.cpp

@@ -1,6 +1,7 @@
 #include "CategoryButton.h"
 #include "Database.h"
 #include "MainWindow.h"
+#include "SplitView.h"
 
 #include <Bitmap.h>
 #include <Catalog.h>
@@ -58,8 +59,13 @@ CategoryButton::MessageReceived(BMessage* msg)
 			BString category;
 			msg->FindString("category", &category);
 			fCategoryBox->SetText(category);
-			fCategoryBox->Validate();
+			bool success = fCategoryBox->Validate();
 
+			if (success) {
+				BMessenger* msgr(fCategoryBox->GetFilter()->GetMessenger());
+				BMessage notice(M_SPLIT_CATEGORY_CHANGED);
+				msgr->SendMessage(&notice);
+			}
 			break;
 		}
 		default: