make uninitialized global and local variables cause exception.

Global.cpp

@@ -80,7 +80,9 @@ namespace jet {
 	 } else {
 	    renderVariableName(variable, name, modifier, lvariables);
 	    name.split(".");
-	    if(name.getList().size() == 1) {	 
+	    if(name.getList().size() == 1) {
+	       if(variables.find(name[0]) == variables.end())
+		 throw coreutils::Exception("global variable is not initialized.");
 	       return processModifier(variables[name[0]], modifier);
 	    }	    
 	    return getSessionVariable(name);
@@ -90,6 +92,8 @@ namespace jet {
 	 coreutils::MString name;
 	 coreutils::MString modifier;
 	 renderVariableName(variable, name, modifier, lvariables);
+	 if(lvariables.find(name) == lvariables.end())
+	   throw coreutils::Exception("local variable is not initialized.");
 	 return lvariables[name];	 
       }
       throw coreutils::Exception("Expecting a variable initializer ('$[' or '#[').");