Bug fix to [esc] key behaviour

- Using [esc] to 'unload' spritesheet works again.
- Added description of [esc] key functionality to new help-text label.

Author: ForkandBeard

ASU/UI/MainForm.Designer.cs

@@ -796,7 +796,14 @@ private void MainPanel_Paint(object sender, System.Windows.Forms.PaintEventArgs
 
                     graphics = Graphics.FromImage(PaintedImage);
                     graphics.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.NearestNeighbor;
-                    graphics.Clear(this.unpackers[0].CreateOuterBackgroundColour());
+                    if (this.unpackers.Count >= 1)
+                    {
+                        graphics.Clear(this.unpackers[0].CreateOuterBackgroundColour());
+                    }
+                    else
+                    {
+                        graphics.Clear(Color.Black);
+                    }
                     graphics.DrawImage(SheetWithBoxes, this.Offset);
 
                     Rectangle boxOffset;
@@ -1547,6 +1554,18 @@ protected override bool ProcessCmdKey(ref System.Windows.Forms.Message msg, Syst
 
             if (keyData == Keys.Escape)
             {
+                if (this.OriginalImage != null)
+                {
+                    this.OriginalImage.Dispose();
+                    this.OriginalImage = null;
+                }
+
+                if (this.PaintedImage != null)
+                {
+                    this.PaintedImage.Dispose();
+                    this.PaintedImage = null;
+                }
+
                 if (this.unpackers.Count == 1 && this.AreAllUnpacked())
                 {
                     this.unpackers.Clear();

ASU/UI/MainForm.cs

@@ -126,6 +126,13 @@
   <metadata name="ImageClipperAndAnimatorTimer.TrayLocation" type="System.Drawing.Point, System.Drawing, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a">
     <value>17, 17</value>
   </metadata>
+  <data name="ControlsHelpLabel.Text" xml:space="preserve">
+    <value>[left click]          select or split frame
+[right click]         toggle select / split mode
+[ctrl + left drag]    select multiple frames
+[cursor keys]         move pointer by single pixel
+[esc]                 unload current sprite sheet</value>
+  </data>
   <assembly alias="System.Drawing" name="System.Drawing, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" />
   <data name="$this.Icon" type="System.Drawing.Icon, System.Drawing" mimetype="application/x-microsoft.net.object.bytearray.base64">
     <value>