Make spyPart shortcut attribute optional

The shortcut attribute on the org.eclipse.pde.spy.core.spyPart extension
point is not declared as required in its schema, but SpyProcessor would
NPE when a contribution omitted it (keySequence.equals in
bindSpyKeyBinding). Skip key-binding registration when no shortcut is
provided so a spy can opt into discoverability via the spy stack toolbar
without claiming a global keystroke.

Author: vogella

ui/org.eclipse.pde.spy.core/forceQualifierUpdate.txt

@@ -1,3 +1,4 @@
 # To force a version qualifier update add the bug here
 https://github.com/eclipse-platform/eclipse.platform.releng.aggregator/issues/1184
-https://github.com/eclipse-platform/eclipse.platform.releng.aggregator/issues/1659
+https://github.com/eclipse-platform/eclipse.platform.releng.aggregator/issues/1659
+https://github.com/eclipse-pde/eclipse.pde/pull/2326

ui/org.eclipse.pde.spy.core/src/org/eclipse/pde/spy/core/SpyProcessor.java

@@ -81,7 +81,9 @@ public void process(IExtensionRegistry extRegistry) {
 				// Bind the command with the binding, and add the view ID as
 				// parameter.
 				// The part class name will be the ID of the part descriptor
-				bindSpyKeyBinding(bindingTable, shortCut, command, partID);
+				if (shortCut != null && !shortCut.isBlank()) {
+					bindSpyKeyBinding(bindingTable, shortCut, command, partID);
+				}
 
 				// Add the descriptor in application
 				addSpyPartDescriptor(partID, partName, iconPath, partClass, desc);