Add a QgsRectangle::createNull() temporary static method

python/core/auto_generated/geometry/qgsrectangle.sip.in

@@ -59,6 +59,7 @@ Copy constructor
 
     ~QgsRectangle();
 
+
     static QgsRectangle fromWkt( const QString &wkt );
 %Docstring
 Creates a new rectangle from a ``wkt`` string.

src/core/geometry/qgsrectangle.h

@@ -99,6 +99,22 @@ class CORE_EXPORT QgsRectangle
     // see https://github.com/qgis/QGIS/pull/4720#issuecomment-308652392
     ~QgsRectangle() = default;
 
+    /**
+    * Creates a null rectangle.
+    *
+    * This is a temporary method to use while the default
+    * constructor is still not constructing a null rectangle.
+    *
+    * \since QGIS 3.34
+    */
+    static QgsRectangle createNull() SIP_SKIP
+    {
+      // TODO: remove this method once the default constructor gives a null
+      QgsRectangle rectNull;
+      rectNull.setNull(); // TODO: have setNull() return *this ?
+      return rectNull;
+    }
+
     /**
     * Creates a new rectangle from a \a wkt string.
     * The WKT must contain only 5 vertices, representing a rectangle aligned with X and Y axes.