Fix segfault with expression bindings on database backends #5161
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In some situations, attribute bindings may cause a segmentation fault, when executing multiple MapScript operations, e.g.
queryByPoint()
followed bydraw()
on the same layer. This is because the expression is tokenized only once - when uninitialized. In case of an attribute binding, the token bindval index points to the sql column-index built from the list of required attributes, in case ofqueryByPoint()
all attributes are requested. A possibly followingdraw()
will reduce the number of attributes to be queried from the database, so the column index in the resultset changes, but the expression token is still the same.The fix is to free the expression object, when
msLayerFreeItemInfo()
is called, which is currently done atLayerClose()
only.