Fix the error with strict = false parameter

Author: Artur Zakirov

expected/pg_variables.out

@@ -1,5 +1,13 @@
 CREATE EXTENSION pg_variables;
 -- Integer variables
+SELECT pgv_get_int('vars', 'int1');
+ERROR:  unrecognized package "vars"
+SELECT pgv_get_int('vars', 'int1', false);
+ pgv_get_int 
+-------------
+            
+(1 row)
+
 SELECT pgv_set_int('vars', 'int1', 101);
  pgv_set_int 
 -------------

pg_variables.c

@@ -132,6 +132,12 @@ variable_get(text *package_name, text *var_name,
 	ScalarVar		   *scalar;
 
 	package = getPackageByName(package_name, false, strict);
+	if (package == NULL)
+	{
+		*is_null = true;
+		return 0;
+	}
+
 	variable = getVariableByNameWithType(package->variablesHash,
 										 var_name, typid, false, strict);