GMS1 IDE is known for being spontaneously allergic to external file changes if the said files have been opened in the IDE.
I’m not aware of any better way around this than reloading the project (File - Recent Projects - (first item)) before running if you’ve added new resources through GMEdit or git. In the last few versions of 1.4 you can also disable thumbnail generation in preferences, which makes the editor load projects much faster.
There once was a plugin to run GMS1 projects from GMEdit, but it could not be used unless you had access to certain non-public versions of the program or performed specific illegal manipulations with your installation - the usual behaviour is that GMS1’s GMAssetCompiler.exe relied on the IDE to validate licenses and thus could not be invoked without it.