Bug 300855 Do not allow Path Variables with empty location
HEAD I'm able to create a path variable without location. Next, when I want to edit the variable, Edit Variable dialog opens with error saying "You must provide a file or folder path as variable value.". I guess I should not be able to create such variable in the first place.
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/internal/ide/dialogs/PathVariableDialog.java
if (operationMode != EDIT_LINK_LOCATION) {
	        
	        variableNameLabel = new Label(contents, SWT.LEAD);
	        variableNameLabel.setText(nameLabelText);
	     
	        
	        variableNameField = new Text(contents, SWT.SINGLE | SWT.BORDER);
	        variableNameField.setText(variableName);
	        variableNameField.setLayoutData(new GridData(SWT.FILL, SWT.CENTER, true,
	        		false, 2, 1));
	        variableNameField.addModifyListener(new ModifyListener() {
	            public void modifyText(ModifyEvent event) {
	                variableNameModified();
	            }
	        });
        }
        
        
        variableValueLabel = new Label(contents, SWT.LEAD);
        variableValueLabel.setText(valueLabelText);
        
        variableValueField = new Text(contents, SWT.SINGLE | SWT.BORDER);
        variableValueField.setText(variableValue);
        variableValueField.setLayoutData(new GridData(SWT.FILL, SWT.CENTER, true,
        		false));
        variableValueField.addModifyListener(new ModifyListener() {
            public void modifyText(ModifyEvent event) {
                variableValueModified();
            }
        });