Hint is can't Float in TextBox and ComboBox when text is only all SPACE. #578 #574

Author: Chi_Xiaohui

MaterialDesignThemes.Wpf/HintProxyFabric.ComboBox.cs

@@ -50,7 +50,7 @@ public object Content
 
             public bool IsEmpty()
             {
-                return string.IsNullOrWhiteSpace(_comboBox.Text);
+                return string.IsNullOrEmpty(_comboBox.Text);
             }
 
             public event EventHandler ContentChanged;

MaterialDesignThemes.Wpf/HintProxyFabric.TextBox.cs

@@ -16,7 +16,7 @@ private sealed class TextBoxHintProxy : IHintProxy
 
             public bool IsVisible => _textBox.IsVisible;
 
-            public bool IsEmpty() => string.IsNullOrWhiteSpace(_textBox.Text);
+            public bool IsEmpty() => string.IsNullOrEmpty(_textBox.Text);
 
             public event EventHandler ContentChanged;
             public event EventHandler IsVisibleChanged;