Work around harmless g++ warning about possible uninitialized variable.

Return from the function before using the variables in the (impossible) case
they are actually not initialized.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@73887 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/generic/timectrlg.cpp

@@ -480,6 +480,7 @@ private:
                 case Field_AMPM:
                 case Field_Max:
                     wxFAIL_MSG( "Invalid field" );
+                    return;
             }
 
             // Check if the new value is acceptable. If not, we just handle