'project dependency-add' allows additon of invalid dependencies

[prettyfaces-forge-plugin] pf-forge-plugin $ project dependency-add
[[ groupId :artifactId {:version :scope :packaging} ] (of type org.jboss.seam.forge.project.dependencies.Dependency)]

[prettyfaces-forge-plugin] pf-forge-plugin $ project dependency-add 'com.ocpsoft:prettyfaces-jsf2'
Added dependency [com.ocpsoft:prettyfaces-jsf2]
[prettyfaces-forge-plugin] pf-forge-plugin $ project dependency-
dependency-add dependency-list dependency-search dependency-remove
[prettyfaces-forge-plugin] pf-forge-plugin $ project dependency-remove
[[ groupId :artifactId {:version :scope :packaging} ] (of type org.jboss.seam.forge.project.dependencies.Dependency)]

[prettyfaces-forge-plugin] pf-forge-plugin $ project dependency-remove com.ocpsoft:prettyfaces-jsf2
**ERROR** [dependency-remove] org.apache.maven.project.ProjectBuildingException: 2 problems were encountered while building the effective model for com.ocpsoft.forge.prettyfaces:prettyfaces-forge-plugin:1.0.0-SNAPSHOT
[WARNING] 'build.plugins.plugin.version' for org.apache.maven.plugins:maven-compiler-plugin is missing. @ line 30, column 15
[ERROR] 'dependencies.dependency.version' for com.ocpsoft:prettyfaces-jsf2:jar is missing. @ line 17, column 17
for project com.ocpsoft.forge.prettyfaces:prettyfaces-forge-plugin:1.0.0-SNAPSHOT at /home/lb3/Projects/pf-forge-plugin/pom.xml
[prettyfaces-forge-plugin] pf-forge-plugin $ edit pom.xml