xGGQRCS: ensure leading dimension is at least one

Ensure the leading dimension of the assembled matrix `G = [A; B]` is
always at least one.

Author: christoph-conrads

SRC/cggqrcs.f

@@ -452,7 +452,8 @@ RECURSIVE SUBROUTINE CGGQRCS( JOBU1, JOBU2, JOBX, M, N, P, L,
 *
       SWAPPED = .FALSE.
       L = 0
-      LDG = M + P
+*     The leading dimension must never be zero
+      LDG = MAX( M + P, 1 )
       LDVT = N
       LMAX = MIN( M + P, N )
       IG = 1

SRC/dggqrcs.f

@@ -426,7 +426,8 @@ RECURSIVE SUBROUTINE DGGQRCS( JOBU1, JOBU2, JOBX, M, N, P, L,
 *
       SWAPPED = .FALSE.
       L = 0
-      LDG = M + P
+*     The leading dimension must never be zero
+      LDG = MAX( M + P, 1 )
       LDVT = N
       LMAX = MIN( M + P, N )
       IG = 1

SRC/sggqrcs.f

@@ -426,7 +426,8 @@ RECURSIVE SUBROUTINE SGGQRCS( JOBU1, JOBU2, JOBX, M, N, P, L,
 *
       SWAPPED = .FALSE.
       L = 0
-      LDG = M + P
+*     The leading dimension must never be zero
+      LDG = MAX( M + P, 1 )
       LDVT = N
       LMAX = MIN( M + P, N )
       IG = 1

SRC/zggqrcs.f

@@ -451,7 +451,8 @@ RECURSIVE SUBROUTINE ZGGQRCS( JOBU1, JOBU2, JOBX, M, N, P, L,
 *
       SWAPPED = .FALSE.
       L = 0
-      LDG = M + P
+*     The leading dimension must never be zero
+      LDG = MAX( M + P, 1 )
       LDVT = N
       LMAX = MIN( M + P, N )
       IG = 1