[Defaulttype, Helper] Return empty string instead of zero (sofa-framework#5388)

return empty string instead of null

Author: fredroy

Sofa/framework/DefaultType/src/sofa/defaulttype/typeinfo/NoTypeInfo.h

@@ -103,7 +103,7 @@ class SOFA_DEFAULTTYPE_API NoTypeInfo : public AbstractTypeInfo
     /// Relevant only if this type can be casted to `double`.
     double      getScalarValue (const void*, Index) const override {return 0;}
     /// Get the value at \a index of \a data as a string.
-    std::string getTextValue   (const void*, Index) const override {return 0;}
+    std::string getTextValue   (const void*, Index) const override {return "";}
 
     /// Set the value at \a index of \a data from an integer value.
     void setIntegerValue(void*, Index, long long ) const override {return;}

Sofa/framework/Helper/src/sofa/helper/AdvancedTimer.cpp

@@ -1457,12 +1457,12 @@ std::string AdvancedTimer::getTimeAnalysis(IdTimer id, double time, double delta
     if (curTimer.empty())
     {
         msg_error("AdvancedTimer::end") << "timer[" << id << "] called while begin was not" ;
-        return nullptr;
+        return "";
     }
     if (id != curTimer.top())
     {
         msg_error("AdvancedTimer::end") << "timer[" << id << "] does not correspond to last call to begin(" << curTimer.top() << ")" ;
-        return nullptr;
+        return "";
     }
     type::vector<Record>* curRecords = getCurRecords();
     if (curRecords)