Fix issues reported by SonarQube

src/common/Session.cpp

@@ -286,7 +286,7 @@ void Session::get_palettes_name(const std::string &type, QStringList &list) {
 }
 
 Palette *Session::get_palette(const std::string &type, const std::string &palette_name) {
-    Palette *p, **where_from;
+    Palette *p = NULL, **where_from;
     if( type == "palette" ) {
         p = _palettes_state;
         where_from = &_palettes_state;

src/common/Tools.cpp

@@ -57,7 +57,7 @@
 using namespace std;
 
 bool convert_to_double(const std::string &arg, double *val) {
-    unsigned int nb_read;
+    int nb_read;
     // Try to convert first in the current locale
     sscanf(arg.c_str(), "%lf%n", val, &nb_read);