fix some occurrences where size() is misused as Boolean

- as suggested by @wwmayer: 4d51d1d0b1 (r69648152)

src/Mod/Fem/Gui/Command.cpp

@@ -1817,7 +1817,7 @@ void CmdFemPostPipelineFromResult::activated(int)
         Fem::FemAnalysis* pcAnalysis;
         std::string FeatName = getUniqueObjectName("ResultPipeline");
         auto parents = results[0]->getInList();
-        if (parents.size()) {
+        if (!parents.empty()) {
             for (auto parentObject : parents) {
                 if (parentObject->getTypeId() == Base::Type::fromName("Fem::FemAnalysis")) {
                     pcAnalysis = static_cast<Fem::FemAnalysis*>(parentObject);

src/Mod/Fem/Gui/ViewProviderFemPostObject.cpp

@@ -430,7 +430,7 @@ void ViewProviderFemPostObject::WritePointData(vtkPoints* points, vtkDataArray*
 
     // we must inherit the Scale of parent meshes (for example for clip filters)
     auto parents = pcObject->getInList();
-    if (parents.size()) {
+    if (!parents.empty()) {
         for (auto itParents = parents.begin(); itParents != parents.end(); ++itParents) {
             if ((*itParents)->getTypeId() == Base::Type::fromName("Fem::FemPostPipeline")) {
                 auto vpObject = dynamic_cast<FemGui::ViewProviderFemPostObject*>(

src/Mod/Part/Gui/SectionCutting.cpp

@@ -513,7 +513,7 @@ void SectionCut::startCutting(bool isInitial)
 
         // if the object is part of an App::Part container, the link needs to get the container placement
         auto parents = (*itCuts)->getInList();
-        if (parents.size()) {
+        if (!parents.empty()) {
             for (auto itParents = parents.begin(); itParents != parents.end(); ++itParents) {
                 if ((*itParents)->getTypeId() == Base::Type::fromName("App::Part")) {
                     App::Part* pcPartParent = static_cast<App::Part*>((*itParents));

src/Mod/Part/Gui/TaskAttacher.cpp

@@ -972,7 +972,8 @@ void TaskAttacher::visibilityAutomation(bool opening_not_closing)
                     QString::fromLatin1(editSubName.c_str()),
                     QString::fromLatin1(postfix.c_str()));
             Gui::Command::runCommand(Gui::Command::Gui,code.toLatin1().constData());
-        } else if(postfix.size()) {
+        }
+        else if (!postfix.empty()) {
             QString code = QString::fromLatin1(
                 "_tv_%1.restore()\n"
                 "del(_tv_%1)"

src/Mod/PartDesign/App/FeatureSketchBased.cpp

@@ -167,7 +167,7 @@ Part::Feature* ProfileBased::getVerifiedObject(bool silent) const {
 Part::TopoShape ProfileBased::getProfileShape() const
 {
     auto shape = getTopoShape(Profile.getValue());
-    if (!shape.isNull() && Profile.getSubValues().size()) {
+    if (!shape.isNull() && !Profile.getSubValues().empty()) {
         std::vector<Part::TopoShape> shapes;
         for (auto& sub : Profile.getSubValues(true))
             shapes.emplace_back(shape.getSubShape(sub.c_str()));

src/Mod/PartDesign/App/ShapeBinder.cpp

@@ -479,17 +479,17 @@ void SubShapeBinder::update(SubShapeBinder::UpdateOption options) {
     if(!Relative.getValue()) 
         parent = nullptr;
     else {
-        if(parent && parent->getSubObject(parentSub.c_str())==this) {
+        if (parent && parent->getSubObject(parentSub.c_str())==this) {
             auto parents = parent->getParents();
-            if(parents.size()) {
+            if (!parents.empty()) {
                 parent = parents.begin()->first;
                 parentSub = parents.begin()->second + parentSub;
             }
         } else
             parent = nullptr;
-        if(!parent && parentSub.empty()) {
+        if (!parent && parentSub.empty()) {
             auto parents = getParents();
-            if(parents.size()) {
+            if(!parents.empty()) {
                 parent = parents.begin()->first;
                 parentSub = parents.begin()->second;
             }
@@ -561,7 +561,7 @@ void SubShapeBinder::update(SubShapeBinder::UpdateOption options) {
                 auto tmpDoc = App::GetApplication().newDocument(
                                 "_tmp_binder", nullptr, false, true);
                 auto objs = tmpDoc->copyObject({obj},true,true);
-                if(objs.size()) {
+                if (!objs.empty()) {
                     for(auto it=objs.rbegin(); it!=objs.rend(); ++it)
                         _CopiedObjs.emplace_back(*it);
                     copied = objs.back();
@@ -648,7 +648,7 @@ void SubShapeBinder::update(SubShapeBinder::UpdateOption options) {
 
     if(!init) {
 
-        if(errMsg.size()) {
+        if (!errMsg.empty()) {
             if(!(options & UpdateInit))
                 FC_THROWM(Base::RuntimeError, errMsg);
             if(!Shape.getValue().IsNull())
@@ -706,7 +706,7 @@ void SubShapeBinder::update(SubShapeBinder::UpdateOption options) {
                 else 
                     solids.push_back(s.getShape());
             }
-            if(solids.size()) {
+            if (!solids.empty()) {
                 result = solid.fuse(solids);
                 fused = true;
             } else if (!solid.isNull()) {
@@ -819,7 +819,7 @@ void SubShapeBinder::onChanged(const App::Property *prop) {
         if(prop == &Support) {
             clearCopiedObjects();
             setupCopyOnChange();
-            if(Support.getSubListValues().size()) {
+            if (!Support.getSubListValues().empty()) {
                 update(); 
                 if(BindMode.getValue() == 2)
                     Support.setValue(nullptr);