dg_mosaic: Add incorrect image placement check
dg_mosaic: Add incorrect image placement check

See if we are trying to insert more than one image to a line location.

njwilson23/StereoPipeline,ScottMcMichael/StereoPipeline,oleg-alexandrov/StereoPipeline,ScottMcMichael/StereoPipeline,DougFirErickson/StereoPipeline,oleg-alexandrov/StereoPipeline,njwilson23/StereoPipeline,NeoGeographyToolkit/StereoPipeline,aaronknister/StereoPipeline,DougFirErickson/StereoPipeline,ScottMcMichael/StereoPipeline,aaronknister/StereoPipeline,njwilson23/StereoPipeline,NeoGeographyToolkit/StereoPipeline,ScottMcMichael/StereoPipeline,NeoGeographyToolkit/StereoPipeline,oleg-alexandrov/StereoPipeline,aaronknister/StereoPipeline,ScottMcMichael/StereoPipeline,aaronknister/StereoPipeline,aaronknister/StereoPipeline,NeoGeographyToolkit/StereoPipeline,DougFirErickson/StereoPipeline,njwilson23/StereoPipeline,NeoGeographyToolkit/StereoPipeline,oleg-alexandrov/StereoPipeline,njwilson23/StereoPipeline,oleg-alexandrov/StereoPipeline,DougFirErickson/StereoPipeline,NeoGeographyToolkit/StereoPipeline,DougFirErickson/StereoPipeline,oleg-alexandrov/StereoPipeline,DougFirErickson/StereoPipeline,ScottMcMichael/StereoPipeline,njwilson23/StereoPipeline