Fix nimIdentNormalize, fixes #19067 (#19068)

* Make nimIdentNormalize return "" when passed ""; fixes #19067

Fixes #19067

* Add tests for nimIdentNormalize

(cherry picked from commit ee703c5)

Author: EliteTK

lib/pure/strutils.nim

@@ -276,8 +276,9 @@ func nimIdentNormalize*(s: string): string =
   runnableExamples:
     doAssert nimIdentNormalize("Foo_bar") == "Foobar"
   result = newString(s.len)
-  if s.len > 0:
-    result[0] = s[0]
+  if s.len == 0:
+    return
+  result[0] = s[0]
   var j = 1
   for i in 1..len(s) - 1:
     if s[i] in {'A'..'Z'}:

tests/stdlib/tstrutils.nim

@@ -841,5 +841,12 @@ bar
     doAssert s.endsWith('a') == false
     doAssert s.endsWith('\0') == false
 
+  block: # nimIdentNormalize
+    doAssert nimIdentNormalize("") == ""
+    doAssert nimIdentNormalize("foo") == "foo"
+    doAssert nimIdentNormalize("foo_bar") == "foobar"
+    doAssert nimIdentNormalize("Foo_bar") == "Foobar"
+    doAssert nimIdentNormalize("_Foo_bar") == "_foobar"
+
 static: main()
 main()