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
/**
     * Returns the variable name.
     * 
     * @return the variable name
     */
    public String getVariableName() {
        return variableName;
    }
    /**
     * Returns the variable value.
     * 
     * @return the variable value
     */
    public String getVariableValue() {
    	if (currentResource != null) {
    		String internalFormat = getPathVariableManager().convertFromUserEditableFormat(variableValue, operationMode == EDIT_LINK_LOCATION, currentResource);
    		return internalFormat;
    	}
    	return variableValue;
    }
    /**
     * Sets the variable name.
     * 
     * @param variableName the new variable name
     */
    public void setVariableName(String variableName) {
        this.variableName = variableName.trim();
        this.originalName = this.variableName;
    }
    /**