Base: Add isNullOrEmpty string helper

This adds isNullOrEmpty string helper that cheks if string is... well
null or empty. It is done to improve readability of the code and better
express intent.

src/Base/ConsoleObserver.cpp

@@ -35,6 +35,7 @@
 
 #include "ConsoleObserver.h"
 #include "Interpreter.h"
+#include "Tools.h"
 
 
 using namespace Base;
@@ -343,7 +344,7 @@ std::stringstream& LogLevel::prefix(std::stringstream& str, const char* src, int
 #endif
         }
     }
-    if (print_src && src && src[0]) {
+    if (print_src && !Base::Tools::isNullOrEmpty(src)) {
 #ifdef FC_OS_WIN32
         const char* _f = std::strrchr(src, '\\');
 #else

src/Base/FileInfo.cpp

@@ -45,6 +45,7 @@
 #include "Exception.h"
 #include "Stream.h"
 #include "TimeInfo.h"
+#include "Tools.h"
 
 
 using namespace Base;
@@ -119,7 +120,7 @@ const std::string& FileInfo::getTempPath()
         delete[] dest;
 #else
         const char* tmp = getenv("TMPDIR");
-        if (tmp && tmp[0] != '\0') {
+        if (!Base::Tools::isNullOrEmpty(tmp)) {
             tempPath = tmp;
             FileInfo fi(tempPath);
             if (tempPath.empty() || !fi.isDir()) {  // still empty or non-existent

src/Base/ParameterPy.cpp

@@ -42,6 +42,8 @@
 #include "Exception.h"
 #include "Interpreter.h"
 
+#include <Tools.h>
+
 
 namespace Base
 {
@@ -73,7 +75,7 @@ public:
             Py::Tuple args(2);
             args.setItem(0, Py::asObject(GetPyObject(hGrp)));
             // A Reason of null indicates to clear the parameter group
-            if (Reason && Reason[0] != '\0') {
+            if (!Base::Tools::isNullOrEmpty(Reason)) {
                 args.setItem(1, Py::String(Reason));
             }
             method.apply(args);

src/Base/Tools.h

@@ -301,6 +301,11 @@ struct BaseExport Tools
      */
     static std::string quoted(const std::string&);
 
+    static constexpr bool isNullOrEmpty(const char* str)
+    {
+        return !str || str[0] == '\0';
+    }
+
     /**
      * @brief joinList
      * Join the vector of strings \a vec using the separator \a sep