[App] [Spreadsheet] fix compilation errors

- introduced by #7318 and #7319

src/App/ObjectIdentifier.cpp

@@ -1685,7 +1685,7 @@ Py::Object ObjectIdentifier::access(const ResolveResults &result,
         auto &propset = (*deps)[obj];
         // inserting a blank name in the propset indicates the dependency is
         // on all properties of the corresponding object.
-        if (propset.size() != 1 || !propset.begin()->->empty()) {
+        if (propset.size() != 1 || !propset.begin()->empty()) {
             if (!propName) {
                 propset.clear();
                 propset.insert("");

src/Mod/Spreadsheet/App/Sheet.cpp

@@ -208,7 +208,7 @@ bool Sheet::importFromFile(const std::string &filename, char delimiter, char quo
                 tokenizer<escaped_list_separator<char> > tok(line, e);
 
                 for(tokenizer<escaped_list_separator<char> >::iterator i = tok.begin(); i != tok.end();++i) {
-                    if (!*i.empty())
+                    if ((*i).size() > 0)
                         setCell(CellAddress(row, col), (*i).c_str());
                     col++;
                 }

src/Mod/Spreadsheet/App/SheetPyImp.cpp

@@ -622,7 +622,7 @@ PyObject* SheetPy::setAlignment(PyObject *args)
         tokenizer<escaped_list_separator<char> > tok(line, e);
 
         for(tokenizer<escaped_list_separator<char> >::iterator i = tok.begin(); i != tok.end();++i) {
-            if(!i->->empty())
+            if(!i->empty())
                 alignment = Cell::decodeAlignment(*i, alignment);
         }
     }