If the specified GDC coefficient file does not exist, act as if it was never specified.

bb_pipeline_tools/bb_pipeline_queue.py

@@ -196,6 +196,10 @@ def main():
     elif coeff == "prisma":
         coeff = os.environ['BB_BIN_DIR'] + "/bb_data/bb_GDC_coeff_prisma.grad"
 
+    if not os.path.exists(coeff):
+        coeff = none
+
+
     # Parsing number of SWI coils argument
     if not argsa.coils_SWI:
         coils_SWI = 32