[Bug]: subplot_mosaic bug with empty_sentinel and sharey=True #25417

from matplotlib import pyplot as plt
import numpy as np

data = [ np.array( [ i for i in range( 100 ) ] ) , np.random.random( 100 ) ]

fig1 = plt.figure()

# create a mosaic with an empty_sentinel 
# at the END of the row. 
# 'sharey=True' works.
subplots = fig1.subplot_mosaic(
        """
        AB.
        CDE
        """ , sharex = True , sharey = True )

subplots[ "A" ].plot( data[0] , data[1] )
subplots[ "B" ].plot( data[0] , data[1] )
subplots[ "C" ].plot( data[0] , data[1] )
subplots[ "D" ].plot( data[0] , data[1] )
subplots[ "E" ].plot( data[0] , data[1] )

subplots[ "C" ].set_xlabel( 'A variable' )
subplots[ "D" ].set_xlabel( 'A variable' )
subplots[ "E" ].set_xlabel( 'A variable' )

subplots[ "A" ].set_ylabel( 'Some data' )
subplots[ "C" ].set_ylabel( 'Some data' )

plt.savefig( 'mosaic_working.pdf' )

# create a mosaic with an empty_sentinel 
# at the start of the row. 
# 'sharey=True' DOESN'T work: the y ticks
# are missing.
fig2 = plt.figure()

subplots = fig2.subplot_mosaic(
        """
        .AB
        CDE
        """ , sharey = True )

subplots[ "A" ].plot( data[0] , data[1] )
subplots[ "B" ].plot( data[0] , data[1] )
subplots[ "C" ].plot( data[0] , data[1] )
subplots[ "D" ].plot( data[0] , data[1] )
subplots[ "E" ].plot( data[0] , data[1] )

subplots[ "C" ].set_xlabel( 'A variable' )
subplots[ "D" ].set_xlabel( 'A variable' )
subplots[ "E" ].set_xlabel( 'A variable' )

subplots[ "A" ].set_ylabel( 'Some data' )
subplots[ "C" ].set_ylabel( 'Some data' )

plt.savefig( 'mosaic_not_working.pdf' )