Added a test case for printing an empty string (#2590)

Fixes #2364 according to issue description

test_conformance/printf/util_printf.cpp

@@ -1032,6 +1032,9 @@ testCase testCaseChar = {
 
 std::vector<printDataGenParameters> printStringGenParameters = {
 
+    // empty format, no data representation
+    { {""} },
+
     // empty format
     { {""}, "\"foo\"" },
 
@@ -1094,6 +1097,8 @@ std::vector<std::string> correctBufferString = {
 
     "",
 
+    "",
+
     " foo",
 
     "f",