FIX: Fixed exception in Input Action Asset Editor window when typing whitespace into the search field. (#838)

Author: jechter

Packages/com.unity.inputsystem/CHANGELOG.md

@@ -12,6 +12,7 @@ however, it has to be formatted properly to pass verification tests.
 ### Fixed
 
 - Exceptions in scenes of `Visualizers` sample if respective device was not present on system (e.g. in `PenVisualizer` if no pen was present in system).
+- Fixed exception in Input Action Asset Editor window when typing whitespace into the search field.
 - Fixed control scheme popup window in input action asset editor window showing in the correct screen position on windows.
 
 #### Actions

Packages/com.unity.inputsystem/InputSystem/Utilities/StringHelpers.cs

@@ -173,6 +173,9 @@ public static IEnumerable<Substring> Tokenize(this string str)
                 while (pos < length && char.IsWhiteSpace(str[pos]))
                     ++pos;
 
+                if (pos == length)
+                    break;
+
                 if (str[pos] == '"')
                 {
                     ++pos;