[mssql] Ignore unset attributes when changing attribute values, addin…

…g features

src/providers/mssql/qgsmssqlprovider.cpp

@@ -1202,6 +1202,9 @@ bool QgsMssqlProvider::addFeatures( QgsFeatureList &flist, Flags flags )
       if ( fld.name().isEmpty() )
         continue; // invalid
 
+      if ( attrs.at( i ).userType() == qMetaTypeId< QgsUnsetAttributeValue >() )
+        continue;
+
       if ( mDefaultValues.contains( i ) && mDefaultValues.value( i ) == attrs.at( i ).toString() )
         continue; // skip fields having default values
 
@@ -1300,6 +1303,9 @@ bool QgsMssqlProvider::addFeatures( QgsFeatureList &flist, Flags flags )
       if ( fld.name().isEmpty() )
         continue; // invalid
 
+      if ( attrs.at( i ).userType() == qMetaTypeId< QgsUnsetAttributeValue >() )
+        continue;
+
       if ( mDefaultValues.contains( i ) && mDefaultValues.value( i ) == attrs.at( i ).toString() )
         continue; // skip fields having default values
 
@@ -1554,6 +1560,9 @@ bool QgsMssqlProvider::changeAttributeValues( const QgsChangedAttributesMap &att
       if ( fld.name().isEmpty() )
         continue; // invalid
 
+      if ( it2.value().userType() == qMetaTypeId< QgsUnsetAttributeValue >() )
+        continue;
+
       if ( mComputedColumns.contains( fld.name() ) )
         continue; // skip computed columns because they are done server side.
 
@@ -1593,6 +1602,9 @@ bool QgsMssqlProvider::changeAttributeValues( const QgsChangedAttributesMap &att
       if ( fld.name().isEmpty() )
         continue; // invalid
 
+      if ( it2.value().userType() == qMetaTypeId< QgsUnsetAttributeValue >() )
+        continue;
+
       if ( mComputedColumns.contains( fld.name() ) )
         continue; // skip computed columns because they are done server side.