Check for view presence in wxDocument::RemoveView()

Return false and avoid calling OnChangedViewList() if the view wasn't present
in the first place.

This is not, strictly speaking, backwards compatible, but most of the existing
code doesn't seem to check the return value of RemoveView() at all and it's
hard to imagine that someone would rely on it returning true when removing a
non-existent view, so in practice this changes seems to be safe.

Closes #17888.

interface/wx/docview.h

@@ -1530,8 +1530,12 @@ public:
     virtual bool OnSaveModified();
 
     /**
-        Removes the view from the document's list of views, and calls
-        OnChangedViewList().
+        Removes the view from the document's list of views.
+
+        If the view was really removed, also calls OnChangedViewList().
+
+        @return @true if the view was removed or @false if the document didn't
+            have this view in the first place.
     */
     virtual bool RemoveView(wxView* view);
 

src/common/docview.cpp

@@ -570,7 +570,9 @@ bool wxDocument::AddView(wxView *view)
 
 bool wxDocument::RemoveView(wxView *view)
 {
-    (void)m_documentViews.DeleteObject(view);
+    if ( !m_documentViews.DeleteObject(view) )
+        return false;
+
     OnChangedViewList();
     return true;
 }